Touch sensor with front panel

ABSTRACT

A front panel for a touch sensor, which comprises a transparent substrate, and a high resistance layer and an insulating layer having electrical insulating properties stacked in this order on the transparent substrate, wherein the surface resistivity of the high resistance layer is from 1 to 100 MΩ/□, and the luminous transmittance of the front plate for a touch sensor is at least 80%.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a front panel for a touch sensor to beprovided in front of a touch panel display device provided with aso-called touch sensor to feed back the sense of touch to the fingertipof a user.

2. Discussion of Background

In recent years, a touch panel display device (interface device)provided with a touch panel display operated by directly touching atouch panel by fingers or the like has been used as an input device oran input/output device.

A touch panel display device used as an input device or an input/outputdevice is advantageous in that an input screen can be freely constitutedby use of software, and it therefore has a flexibility which can not beobtained with an input device constituted by use of mechanical switches,and in addition, it can be constituted to be light in weight and compactin form, and is low in frequency of occurrence of mechanical failures.Due to these advantageous, at present, touch panel display devices arewidely used ranging from operation panels for relatively large machinesto input/output devices for very small portable apparatus.

Many of touch panel display devices are so designed that the user'sfingertip operating the touch panel display device only touches a flatand smooth panel surface. Therefore, the touch panel display devices donot give a click feeling such as those sensed by a fingertip operatingan input device constituted by use of mechanical switches. This has beenthe cause of the indefinite feeling in operating a touch panel displaydevice. To solve this problem, a touch panel display device providedwith a so-called touch sensor, in which the sense of touch is fed backto the user's fingertip operating the touch panel display has beenproposed (for example, Patent Document 1). The touch panel displaydevice is so configured that a touch panel touched by the user'sfingertip is vibrated, whereby the sense of touch is generated for theuser.

In addition to one so designed that the sense of touch is fed back bythe mechanical stimulation, a technique to give the sense of touch forthe user by an electrical sense by controlling the electric charge of aprotective film or the like (hereinafter referred to as a front panel)to be provided in front of a touch panel has been known (for example,Patent Document 2). In Patent Document 2, to conducting electrodes eachprovided with an insulator, a predetermined electrical input is appliedfrom a voltage source to form electrostatic force (capacitive coupling)in a region between the conducting electrodes and the body, whereby anelectrical sense is generated.

As such a constitution, for example, Non-Patent Document 1 discloses atouch panel having a transparent electrode stacked on a glass substrate,covered with an insulating layer.

A device as disclosed in Patent Document 2 or Non-Patent Document 1 isspecifically, as shown in FIG. 1, so constituted that the voltage andthe frequency are controlled in a pattern capable of reproducing thetactile feeling to be expressed, and electricity is applied to atransparent electrode (not shown) on a touch panel main body 100 from acontrol part not shown, and the electric charge induced on a front panel101 side is accumulated on a layer 103 formed on a transparent substrate102, so that the front panel 101 will be charged. When a sensoryreceptor X such as a finger is contacted to the surface of the frontpanel 101 in such a charged state, a weak electrostatic force worksbetween them by means of an insulating layer 104, which is perceived bythe sensory receptor X as the tactile feeling such as a concave-convextouch feeling.

As a front panel to be provided on such a touch panel display deviceprovided with a so-called touch sensor, one which will not inhibit theoperation of the transparent substrate provided on the touch panel mainbody, which accurately develops the charged state based on the voltageor the frequency fed from the control unit, and which can develop thedesired sense of touch with good reproducibility, has been desired, andit has been desired to control the resistivity of the layer 103 on whichthe electric charge is to be accumulated precisely within apredetermined range.

On the other hand, the front panel is required to have a high lighttransmittance and a low reflectance to light in the visible range inorder to secure the visibility, as it is provided in front of the touchpanel main body which shows images. Further, the front panel of thetouch panel is required to have a hardness which can withstand a certainlevel of pressing force and have a moderate smoothness, since it isoperated by being pressed or rubbed directly by fingers or the like.

However, a front panel to be provided on such a touch panel, whichexcellently develops the sense of touch, which has a favorable lighttransmittance and a low reflectance to light in the visible region, andwhich has sufficient hardness and smoothness as well, has not yet beenobtained, and accordingly no accurate sensor precision can be obtained,or the visibility or the operability is poor.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-A-2003-288158

Patent Document 2: JP-A-2009-87359

Non-Patent Document

Non-Patent Document 1:

http://www.disneyresearch.com/research/projects/teslatouchuist2010.pdf

SUMMARY OF INVENTION

The present invention has been made to solve the above problems, and itsobject is to provide a front panel for a touch sensor which has afavorable sensor accuracy perceived by the sense of touch, which has ahigh light transmittance and a low reflectance to light in the visibleregion, and which is excellent in the visibility and the operability.

The front panel for a touch sensor of the present invention is a frontpanel for a touch sensor, which comprises a transparent substrate, and ahigh resistance layer and an insulating layer having electricalinsulating properties stacked in this order on the transparentsubstrate, wherein the surface resistivity of the high resistance layeris from 1 to 100 MΩ/□, and the luminous transmittance of the front platefor a touch sensor is at least 85%.

The front panel for a touch sensor is preferably such that the staticfriction coefficient is at most 0.2. Further, it is preferred that abarrier layer is interposed between the transparent substrate and thehigh resistance layer. Further, the front panel for a touch sensor ispreferably such that the water contact angle is at least 80°. Further,the front panel for a touch sensor is preferably such that the luminousreflectance is at most 2%.

The front panel for a touch sensor of the present invention, whichcomprises a transparent substrate, and a high resistance layer and aninsulating layer stacked in this order on the transparent substrate, bythe surface resistivity of the high resistance layer being from 1 to 100MΩ/□, and the luminous transmittance of the front panel for a touchsensor being at least 85%, has a favorable sensor accuracy perceived bythe sense of touch and is excellent in the visibility and theoperability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating a state where a fingertip isclose to the surface of a touch panel provided with a front panel for atouch sensor.

FIG. 2 is a cross sectional view schematically illustrating one exampleof a front panel for a touch sensor of the present invention.

FIG. 3 is a cross sectional view schematically illustrating a statewhere the front panel for a touch sensor shown in FIG. 1 is stackedabove a touch panel main body.

FIG. 4 is a cross sectional view schematically illustrating one exampleof a front panel for a touch sensor of the present invention.

FIG. 5 is a cross sectional view schematically illustrating one exampleof a front panel for a touch sensor of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, embodiments of the front panel for a touch sensor of the presentinvention will be described.

FIG. 2 is a cross sectional view schematically illustrating one exampleof a front panel for a touch sensor.

A front panel 1 for a touch sensor comprises a transparent substrate 2,and a high resistance layer 3 and an insulating layer 4 stacked in thisorder on the transparent substrate 2.

The transparent substrate 2 is not particularly limited so long as it issmooth and is transparent to light in the visible region.

Specifically, it may, for example, be a transparent glass plate made ofglass such as transparent and colorless soda lime silicate glass,aluminosilicate glass (SiO₂—Al₂O₃—Na₂O type glass), lithiumaluminosilicate glass, quartz glass or alkali-free glass, a plastic filmconsisting of a single layer of a plastic material selected frompolyethylene terephthalate, polycarbonate, triacetyl cellulose,polyether sulfone, polymethyl methacrylate, a cycloolefin polymer andthe like, or a plastic film such as a laminate film comprising two ormore layers of the above plastic materials laminated.

The transparent substrate 2 is preferably a soda lime silicate glassplate from the viewpoint of the adhesion to a layer to be providedthereon. Further, it is preferably a tempered glass plate obtained bytempering an aluminosilicate glass plate (for example, “Dragontrail(registered trademark)”), in view of the strength of the transparentsubstrate 2 itself.

Considering the use pattern of the front panel 1 for a touch sensor, thetransparent substrate 2 is preferably a tempered glass plate obtained bytempering an aluminosilicate glass plate, as it is required to have asufficient strength to withstand a certain level of pressing force.

The glass material constituting the aluminosilicate glass plate may, forexample, be a glass material having a composition comprising, asrepresented by mol %, from 50 to 80% of SiO₂, from 1 to 20% of Al₂O₃,from 6 to 20% of Na₂O, from 0 to 11% of K₂O, from 0 to 15% of MgO, from0 to 6% of CaO and from 0 to 5% of ZrO₂.

On the surface of a tempered glass plate obtained by tempering analuminosilicate glass, a compressive stress layer is formed, and thethickness of the compressive stress layer is preferably at least 10 μm,more preferably at least 30 μm. Further, the surface compressive stressof the compressive stress layer is preferably at least 200 MPa, morepreferably at least 550 MPa.

The method of applying a chemical tempering treatment to analuminosilicate glass plate may be typically a method of immersing analuminosilicate glass plate in a KNO₃ molten salt to carry out ionexchange treatment, and then cooling it to the vicinity of roomtemperature. Treatment conditions such as the temperature of the KNO₃molten salt and the immersion time are set so that desired surfacecompressive stress and thickness of the compressive stress layer areobtained.

The thickness of the transparent substrate 2 is not particularlylimited, and is preferably from 0.1 to 2.0 mm, more preferably from 0.3to 1 mm, in a case where the transparent substrate 2 is constituted bythe above-described glass substrate. When the thickness of thetransparent substrate 2 is at most 2 mm, the pressing force applied tothe surface of the front panel 1 for a touch sensor will easily betransmitted to the panel main body located below the front panel, thusleading to favorable operability. In a case where the transparentsubstrate 2 is constituted by the above-described plastic film, itsthickness is preferably from 50 to 500 μm, more preferably from 50 to200 μm.

The transparent substrate 2 may be constituted by a single layer or maybe constituted by a plurality of layers.

The high resistance layer 3 is a layer having a surface resistivity offrom 1 to 100 MΩ/□, and it may, for example, be a layer on which theelectric charge induced on the side of the front panel 1 for a touchsensor by applying electricity to transparent electrodes 5 a provided ona touch panel main body 5 (see FIG. 3) disposed below the transparentsubstrate 2 is to be accumulated.

The constitution of the high resistance layer 3 is not particularlylimited so long as it has a surface resistivity within the above range.For example, a layer containing tin oxide and titanium oxide as the maincomponents or a layer containing niobium oxide and titanium oxide as themain components may be suitably used.

When the surface resistivity of the high resistance layer 3 is at least1 MΩ/□, it is possible to prevent the operation of the touch panel mainbody 5 from being inhibited by electrical interaction of the highresistance layer 3 with the transparent electrodes 5 a when electricityis applied to the transparent electrodes 5 a of the touch panel mainbody 5. Further, when the surface resistivity of the high resistancelayer 3 is at most 100 MΩ/□, the charged state based on the controlvoltage and the frequency is accurately developed, whereby the desiredsense of touch can be developed with good reproducibility to the sensoryreceptor X, whereby an excellent sensor accuracy by the sense of touchcan be obtained. The surface resistivity of the high resistance layer 3is preferably from 5 to 60 MΩ/□.

The high resistance layer 3 is preferably a layer containing tin oxideand titanium oxide as the main components, whereby the surfaceresistivity can easily be controlled to be within the above preferredrange, while a favorable luminous transmittance and a low luminousreflectance are secured.

The layer containing tin oxide and titanium oxide as the main componentsor the layer containing niobium oxide and titanium oxide as the maincomponents, contains tin oxide and titanium oxide, or niobium oxide andtitanium oxide, as the main components, and may contain another elementsuch as Al, Si, Ga or In within a range not to impair the function ofthe high resistance layer 3.

The high resistance layer 3 may be formed on the transparent substrate 2comprising e.g. a glass substrate, by sputtering such as DC (directcurrent) sputtering, AC (alternate current) sputtering or RF(radio-frequency) sputtering. Among them, DC magnetron sputtering issuitably used, since the process is stably conducted and film formationon a large area is easy.

Here, DC magnetron sputtering includes pulsed (a voltage is applied in apulse waveform) DC magnetron sputtering. Pulsed DC magnetron sputteringis effective to prevent abnormal electric discharge.

The high resistance layer 3 is preferably one containing at least twometal elements, such as the above-described layer containing tin oxideand titanium oxide as the main components, whereby the surfaceresistivity will easily be controlled to be within the above preferredrange, while it has a favorable light transmittance. For formation ofsuch a high resistance layer 3, a so-called co-sputtering employing aplurality of targets each comprising a single element can be employed.

For example, in a case where a layer containing tin oxide and titaniumoxide as the main components is to be formed by co-sputtering, astargets, a target containing tin as the main component and a targetcontaining titanium as the main component are used.

The metal target containing tin as the main component may be oneconsisting solely of tin, or one containing tin as the main componentdoped with a known metal dopant other than tin, for example, Al or Si,within a range not to impair the effects of the present invention.

The metal target containing titanium as the main component may be oneconsisting solely of titanium, or one containing titanium as the maincomponent doped with a known dopant other than titanium within a rangenot to impair the effects of the present invention.

As the sputtering gas, various reactive gases may be used. Specifically,for example, a mixed gas of an oxygen gas with an inert gas, or a mixedgas of an oxygen gas, a nitrogen gas and an inert gas may be used. Theinert gas may, for example, be a rear gas such as helium, neon, argon,krypton or xenon. Among them, preferred is argon in view of theeconomical efficiency and the easiness of electric discharge. Thesegases may be used alone or as a mixture of two or more. As thesputtering gas, as the gas containing a nitrogen atom, N₂O, NO, NO₂, NH₃or the like may also be used in addition to the nitrogen gas (N₂).

The partial pressures of the oxygen and the inert gas in the sputteringgas and the total pressure of the sputtering gas are not particularlylimited so long as the glow discharge is stably conducted.

In a case where sputtering is carried out, the power density ispreferably from 0.9 to 4 W/cm², more preferably from 0.9 to 3 W/cm². Thefilm deposition time may be determined depending upon the depositionrate and the desired thickness.

Co-sputtering is to be conducted by simultaneously discharging therespective targets, and by controlling the power density applied to eachtarget and the partial pressure of the sputtering gas, a coating filmhaving a desired composition can be formed.

Formation of the high resistance layer 3 may also be carried out by aphysical vapor deposition method other than sputtering, such as a vacuumdeposition method, an ion beam assisted deposition method or an ionplating method, or a chemical vapor deposition method such as a plasmaCVD method. Sputtering is preferably employed, whereby a uniform filmthickness in a large area can easily be obtained.

In a case where the high resistance layer 3 is a layer containing tinoxide and titanium oxide as the main components, it is preferably alayer containing from 1 to 30 atomic %, more preferably from 5 to 20atomic % of Ti based on the total amount (100 atomic %) of Sn and Ti.Further, in a case where the high resistance layer 3 is a layercontaining niobium oxide and titanium oxide as the main components, itis preferably a layer containing from 90 to 99.9 atomic %, morepreferably from 95 to 99.9 atomic % of Ti based on the total amount (100atomic %) of Nb and Ti.

When the atomic ratio in the high resistance layer 3 is within the aboverange, the high resistance layer 3 is likely to have a surfaceresistivity within the above preferred range and a moderate refractiveindex.

The thickness of the high resistance layer 3 is preferably at least 5 nmand at most 100 nm, more preferably at least 5 nm and at most 50 nm,further preferably at least 5 nm and at most 30 nm. When the thicknessof the high resistance layer 3 is at least 5 nm, a sufficient chargeretention function will be obtained. Further, when the thickness of thehigh resistance layer 3 is at most 100 nm, a favorable luminoustransmittance will be obtained.

In the present specification, the “thickness” of each layer is athickness obtained by measurement by a stylus surface profiler.

The thickness of the high resistance layer 3 can be properly adjusted bythe film deposition rate or the substantial film formation time whensputtering is carried out.

In the front panel 1 for a touch sensor, the refractive index (n) of thehigh resistance layer 3 is preferably from 1.8 to 2.5 with a view toobtaining excellent optical properties such as the luminoustransmittance and the luminous reflectance.

The insulating layer 4 is a layer provided on the high resistance layer3 or on the high resistance layer 3 with another layer interposedtherebetween, and is to prevent the electric current based on theelectric charge accumulated on the high resistance layer 3 from directlyflowing into a sensory receptor X (see FIG. 3) such as a fingertip to becontacted to the surface of the front panel 1 for a touch sensor.

In this specification, the insulating layer 4 is a layer having a volumeresistivity of at least 10¹⁰ Ω·cm. The volume resistivity is a valuemeasured in accordance with JIS C2318-1975.

The insulating layer 4 is not particularly limited so long as it istransparent to light and has electrical insulating properties. Forexample, the after-mentioned layer made of a cured product formed bycuring an ultraviolet curable composition (i) for forming an insulatinglayer or a thermosetting composition (ii) for forming an insulatinglayer by light or heat, may be used.

The ultraviolet curable composition (i) for forming an insulating layermay, for example, be one containing the after-mentioned ultravioletcurable polymerizable monomer (A), or may be one containing it and asthe case requires, an ultraviolet absorber (B) and a photopolymerizationinitiator (C).

At least part of the ultraviolet curable polymerizable monomer (A)(hereinafter referred to as a monomer (A)) is preferably apolyfunctional polymerizable monomer (a-1) (hereinafter referred to asmonomer (a-1)) having at least two acryloryl groups or methacryloylgroups in one molecule.

Hereinafter, both the polymerizable functional groups will be referredto as a (meth)acryloyl group. The same applies to a (meth)acrylate,(meth)acrylic acid and the like.

The polymerizable functional group is preferably an acryloyl group inview of high polymerizability, particularly high polymerizability byultraviolet light. Accordingly, preferred as the following compoundhaving (meth)acryloyl groups is a compound having acryloyl groups.Likewise, in the case of the (meth)acrylate, (meth)acrylic acid and thelike, preferred is a compound having an acryloyl group. In one moleculeof the compound having at least two (meth)acryloyl groups, thepolymerizable functional groups may be different from each other (thatis, at least one acryloyl group and at least one methacryloyl group maybe contained), and preferably all the polymerizable functional groupsare acryloyl groups.

The monomer (A) other than the monomer (a-1) may be a monofunctionalpolymerizable monomer (hereinafter referred to as monomer (a-2)) havingone (meth)acryloyl group in one molecule or a compound having at leastone ultraviolet curable polymerizable functional group other than the(meth)acryloyl group.

The monomer (A) other than the monomer (a-1) is preferably the monomer(a-2), since when the ultraviolet curable polymerizable functional groupis a (meth)acryloyl group, a sufficient ultraviolet curability will beobtained, and such a compound is easily available. Accordingly, themonomer (A) preferably comprises substantially only one or morecompounds having a (meth)acryloyl group(s) including the monomer (a-1).Hereinafter, the description will be made assuming that all the monomers(A) including the monomer (a-1) are compounds having a (meth)acryloylgroup(s).

The monomer (A) may be a compound having a functional group or a bond inaddition to the (meth)acryloyl group(s). For example, it may have ahydroxy group, a 3 o carboxy group, a halogen atom, a urethane bond, anether bond, an ester bond, a thioether bond or an amido bond.Particularly preferred is a (meth)acryloyl group-containing compoundhaving a urethane bond (hereinafter referred to as an acrylic urethane)or a (meth)acrylic acid ester compound having no urethane bond.

The monomer (a-2) is usually a compound having no urethane bond, but themonomer (a-2) is not limited to a compound having no urethane bond. Onthe other hand, the monomer (a-1) may or may not have an urethane bond.The average number of (meth)acryloyl groups in one molecule of themonomer (a-1) is not particularly limited and is preferably from 2 to50, particularly preferably from 2 to 30.

The acrylic urethane is obtainable by a reaction of a compound having a(meth)acryloyl group and a hydroxy group with a compound having anisocyanate group, a reaction of a compound having a (meth)acryloyl groupand an isocyanate group with a compound having a hydroxy group andhaving no (meth)acryloyl group (hereinafter referred to as a hydroxygroup-containing compound), a reaction of a compound having a(meth)acryloyl group and a hydroxy group, a compound having at least twoisocyanate groups (hereinafter referred to as a polyisocyanate) and ahydroxy group-containing compound, or the like.

Hereinafter, the hydroxy group-containing compound (having no(meth)acryloyl group) means a compound having at least two hydroxygroups, unless otherwise specified.

In such compounds, at least two groups each of the (meth)acryloylgroups, the hydroxy groups and the isocyanate groups may be present inone molecule. In the acrylic urethane obtainable by such a reaction, ahydroxy group may be present, but no isocyanate group is preferablypresent.

The hydroxy group-containing compound having at least two hydroxy groupsmay, for example, be a polyhydric alcohol, a polyol having a highmolecular weight as compared with a polyhydric alcohol, or a hydroxygroup-containing vinyl polymer. Such hydroxy group-containing compoundsmay be used in combination of two or more.

An acrylic urethane preferred as the monomer (a-1) is a reaction productof a hydroxy group-containing (poly)pentaerythritol poly(meth)acrylatewith a polyisocyanate. The (poly)pentaerythritol means pentaerythritol,a pentaerythritol multimer such as dipentaerythritol or a mixturecontaining it as the main component, and the average degree ofmultimerization is preferably from about 1 to 4, particularly preferablyfrom about 1.5 to 3.

The poly(meth)acrylate thereof is preferably a compound which is anester having at least two (meth)acryloyl groups and having from about 3to 6 (meth)acryloyl groups on average per one molecule. Here, the(poly)pentaerythritol poly(meth)acrylate has at least about 1 hydroxygroup on average per one molecule. Further, the average number of(meth)acryloyl groups per one molecule of the acrylic urethane as areaction product is preferably at least 4, particularly preferably from8 to 20.

The monomer (a-1) having no urethane bond is preferably a (meth)acrylateof the hydroxy group-containing compound or (meth)acrylic acid adduct ofa polyepoxide. The hydroxy group-containing compound may, for example,be the above-mentioned polyhydric alcohol or high molecular weightpolyol. As specific examples of the monomer (a-1) having no urethanebond, the following compounds may be mentioned.

The following (meth)acrylates of an aliphatic polyhydric alcohols.1,4-Butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, di(meth)acrylate of a C₁₄₋₁₅ long chainaliphatic diol, 1,3-butanediol di(meth)acrylate, ethylene glycoldi(meth)acrylate, diethylene glycol di(meth)acrylate, glyceroltri(meth)acrylate, glycerol di(meth)acrylate, triglyceroldi(meth)acrylate, trimethylolpropane tri(meth)acrylate,ditrimethylolpropane tetra(meth)acrylate, pentaerthritoltri(meth)acrylate, pentaerythritol tetra(meth)acrylate,dipentaerythritol hexa(meth)acrylate, dipentaerythritolpenta(meth)acrylate and a di(meth)acrylate of a diol comprising acondensate of neopentyl glycol and trimethylolpropane.

The following (meth)acrylates of a polyhydric alcohol or a polyhydricphenol having the following aromatic nucleus or triazine ring.Bis(2-(meth)acryloyloxyethyl) bisphenol A, bis(2-(meth)acryloyloxyethyl)bisphenol S, bis(2-(meth)acryloyloxyethyl) bisphenol F,tris(2-(meth)acryloyloxyethyl) isocyanurate, and bisphenol Adi(meth)acrylate.

The following (meth)acrylates of a hydroxy group-containingcompound/alkylene oxide adduct, (meth)acrylates of a hydroxygroup-containing compound/caprolactone adduct, and (meth)acrylates of apolyoxyalkylene polyol. In the following, EO represents ethylene oxide,PO propylene oxide and the value in the bracket [ ] the molecular weightof a polyoxyalkylene polyol. Tri(meth)acrylate of atrimethylolpropane/EO adduct, tri(meth)acrylate of atrimethylolpropane/PO adduct, triethylene glycol di(meth)acrylate,tetraethylene glycol di(meth)acrylate, tripropylene glycoldi(meth)acrylate, hexa(meth)acrylate of a dipentaerythritol/caprolactoneadduct, tri(meth)acrylate of atris(2-hydroxyethyl)isocyanurate/caprolactone adduct, polyethyleneglycol [200 to 1000] di(meth)acrylate, and polypropylene glycol [200 to1000] di(meth)acrylate.

The following carboxylates and phosphates having a (meth)acryloyl group.Bis(acryloyloxyneopentyl glycol) adipate, di(meth)acrylate of neopentylglycol hydroxypivalate ester, di(meth)acrylate of a neopentyl glycolhydroxypivalate ester/caprolactone adduct,bis(2-(meth)acryloyloxyethyl)phosphate, andtris(2-(meth)acryloyloxyethyl)phosphate.

The following (meth)acrylic acid adducts of a polyepoxide (provided thatone molecule of (meth)acrylic acid is added per one epoxy group of thepolyepoxide), and reaction products of glycidyl (meth)acrylate and apolyhydric alcohol or a polyhydric carboxylic acid (provided that atleast two molecules of glycidyl (meth)acrylate are reacted per onemolecule of the polyhydric alcohol or the like). A (meth)acrylic acidadduct of bisphenol A-diglycidyl ether, a vinyl cyclohexenedioxide/(meth)acrylic acid adduct, a dicyclopentadienedioxide/(meth)acrylic acid adduct, a reaction product of glycidyl(meth)acrylate with ethylene glycol, a reaction product of glycidyl(meth)acrylate with propylene glycol, a reaction product of glycidyl(meth)acrylate with diethylene glycol, a reaction product of glycidyl(meth)acrylate with 1,6-hexanediol, a reaction product of glycidyl(meth)acrylate with glycerol, a reaction product of glycidyl(meth)acrylate with trimethylolpropane, and a reaction product ofglycidyl (meth)acrylate with phthalic acid.

The following alkyl ether compounds, alkenyl ether compounds,carboxylate compounds and the like (hereinafter sometimes referred to asmodified products) of the above (meth)acrylate having an unreactedhydroxy group. An alkyl-modified dipentaerythritol penta(meth)acrylate,an alkyl-modified dipentaerythritol tetra(meth)acrylate, analkyl-modified dipentaerythritol tri(meth)acrylate, an allyl ethercompound of a vinyl cyclohexene dioxide/(meth)acrylic acid adduct, amethyl ether compound of a vinyl cyclohexene dioxide/(meth)acrylic acidadduct, and stearic acid-modified pentaerythritol di(meth)acrylate.

Preferred as the monomer (a-1) which is a polyester having at least two(meth)acryloyloxy groups and having no urethane bond is theabove-mentioned (poly)pentaerythritol poly(meth)acrylate. This(poly)pentaerythritol poly(meth)acrylate is a compound having at leasttwo (meth)acryloyloxy groups on average per one molecule, and may or maynot contain a hydroxy group. The degree of multimerization of the(poly)pentaerythritol moiety is preferably from about 1 to 4,particularly preferably from 1.5 to 3. More preferred as the(poly)pentaerythritol poly(meth)acrylate is (poly)pentaerythritolpoly(meth)acrylate having substantially all hydroxy groups of(poly)pentaerythritol converted to (meth)acryloyloxy groups.

The monofunctional polymerizable monomer i.e. the monomer (a-2) may havea functional group such as a hydroxy group or an epoxy group. Preferredas the monofunctional compound is a (meth)acrylic acid ester i.e. a(meth)acrylate.

As a specific monofunctional compound, the following compounds may, forexample, be mentioned. Methyl (meth)acrylate, ethyl (meth)acrylate,butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl(meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, 1,4-butyleneglycol mono(meth)acrylate, ethoxyethyl (meth)acrylate, and a(meth)acrylic acid adduct of phenyl glycidyl ether.

The monomers (a-1) may be used alone or in combination of two or more.It is preferred that at least one monomer (a-1) is a compound havingfrom 2 to 10 (meth)acrylol groups.

The total proportion of the monomer (a-1) in the monomer (A) ispreferably from 20 to 100 mass %, more preferably from 50 to 100 mass %,further preferably from 70 to 100 mass %. When the proportion of themonomer (a-1) is within such a range, sufficient abrasion resistancewill be obtained.

A part or all of the ultraviolet absorber (B) comprises a polymerizableultraviolet absorber (b-1). In a case where the amount of theultraviolet absorber (B) is small, usually the entire amount comprisesthe polymerizable ultraviolet absorber (b-1). That is, in a case wherethe ultraviolet absorber is contained, the amount of the polymerizableultraviolet absorber (b-1) per 100 parts by mass of the monomer (A) ispreferably at least 0.1 part by mass, more preferably at least 1 part bymass. The upper limit is 50 parts by mass, preferably 30 parts by mass.

By use of the polymerizable ultraviolet absorber (b-1), bleeding of theultraviolet absorber on the surface or a remarkable decrease of theabrasion resistance or the like will not occur even if an ultravioletabsorber in a relatively large amount is incorporated in the compositionfor forming an insulating layer.

The polymerizable ultraviolet absorber (b-1) may be at least one memberselected from the following polymerizable benzophenone compounds andpolymerizable benzotriazole compounds.

An ultraviolet absorber other than the polymerizable ultravioletabsorber (b-1) may be used in combination as the ultraviolet absorber(B), but use of such another ultraviolet absorber in a large amount isunfavorable.

The amount of the ultraviolet absorber other than the polymerizableultraviolet absorber (b-1) is preferably at most 20 parts by mass, morepreferably at most 10 parts by mass per 100 parts by mass of the monomer(A).

As the ultraviolet absorber other than the polymerizable ultravioletabsorber (b-1), a non-polymerizable ultraviolet absorber and apolymerizable ultraviolet absorber other than the polymerizableultraviolet absorber (b-1) may be mentioned, but usuallynon-polymerizable ultraviolet absorber (hereinafter referred to asultraviolet absorber (b-2)) is used. The proportion of the ultravioletabsorber other than the polymerizable ultraviolet absorber (b-1) is notparticularly limited, and is preferably from 0 to 80 mass %,particularly preferably from 0 to 50 mass %, in the entire ultravioletabsorber (B).

The amount of use of the entire ultraviolet absorber (B) is preferablyfrom 0 to 50 parts by mass, more preferably from 0 to 30 parts by massper 100 parts by mass of the monomer (A). In a case where the proportionis at most 50 parts by mass, even when the entire amount of theultraviolet absorber (B) comprises the polymerizable ultravioletabsorber (b-1), an obtainable cured coating film (insulating layer) tobe the insulating layer is well cured and has excellent physicalproperties, although it depends on the thickness, the hardness and thelight resistance required for the cured coating film. In a case wherethe ultraviolet absorber (B) is contained in an amount of at least 0.1part by mass, the cured coating film itself has favorable weatherresistance.

A polymerizable benzophenone compound is a compound having at least one(meth)acryloyl group and at least one benzophenone skeleton. Usually, abenzophenone compound having an ultraviolet absorbing power has at leastone hydroxy group on at least one of two benzene rings in thebenzophenone skeleton (usually the hydroxy group is present at the2-position of the benzophenone skeleton).

The polymerizable benzophenone compound also preferably has at least onehydroxy group on at least one of the two benzene rings in thebenzophenone skeleton, in addition to the organic group having a(meth)acryloyl group (hereinafter referred to as a(meth)acryloyl-containing group). This hydroxy group may be present onthe benzene ring to which the (meth)acryloyl-containing group is bonded,or may be present on the other benzene ring. This hydroxy group ispreferably present at the 2-position of the benzophenone skeleton.

In the polymerizable benzophenone compound, usually one(meth)acryloyl-containing group is present. However, at least two(meth)acryloyl-containing groups may be present, and in such a case,they may be present only one of the two benzene rings or may be presenton both the benzene rings. The hydroxy group is preferably present onthe benzene ring on which the (meth)acryloyl-containing group ispresent. Further, in the two benzene rings, at least one substituentother than the (meth)acryloyl-containing group and the hydroxy group maybe present, and such a substituent is preferably a hydrocarbon groupsuch as an alkyl group, an alkoxy group, a halogen atom or the like. Thenumber of carbon atoms in the hydrocarbon group and the alkoxy group ispreferably at most 6.

The (meth)acryloyl-containing group is preferably a (meth)acryloyloxygroup or an organic group represented by the following formula (1):

—X¹—R¹—X²—CO—CR═CH₂  (1)

In the formula (1), R is a hydrogen atom or a methyl group, X¹ is anoxygen atom, —OCONH—, —OCH₂CH(OH)— or a single bond, R¹ is a bivalenthydrocarbon group, and X² is an oxygen atom, —O—(-COCH₂CH₂O—)_(k)- (k isan integer of at least 1), —NH—, or —CH(OH)CH₂O—. Preferably, R is ahydrogen atom, X¹ is an oxygen atom or a single bond, R¹ is a C₁₋₆alkylene group, and X² is an oxygen atom.

Preferred as the (meth)acryloyl-containing group is a (meth)acryloyloxygroup, a (meth)acryloyloxyalkyl group or a ((meth)acryloyloxy)alkoxygroup, and the number of carbon atoms at a moiety other than the(meth)acryloyloxy group in the latter two groups is preferably from 2 to4.

Preferred as the polymerizable benzophenone compound is a2-hydroxybenzophenone having a (meth)acryloyl-containing group at the4-position of a hydroxyphenyl group. This compound is represented by thefollowing formula (2). In the following formula (2), A is theabove-mentioned (meth)acryloyl-containing group, and each of R² and R³is a substituent other than the (meth)acryloyl-containing group.

As specific examples of the polymerizable benzophenone compound, thefollowing compounds may be mentioned.2-Hydroxy-4-(meth)acryloyloxybenzophenone,2-hydroxy-4-(2-(meth)acryloyloxyethoxy)benzophenone,2-hydroxy-4-(2-acryloyloxypropoxy)benzophenone,2,2′-dihydroxy-4-(meth)acryloyloxybenzophenone and2,2′-dihydroxy-4-(2-(meth)acryloyloxyethoxy)benzophenone.

A polymerizable benzotriazole compound is a compound having at least one(meth)acryloyl group and at least one benzotriazole ring. Usually, abenzotriazole compound having an ultraviolet absorbing power has askeleton in which one benzene ring is bonded at the 2-position of abenzotriazole ring. That is, it comprises 2-phenyl benzotriazole as theskeleton. Further, it has a hydroxy group at the 2-position of thephenyl group.

The polymerizable benzotriazole compound is also preferably such acompound comprising 2-phenyl benzotriazole as the skeleton and having ahydroxy group at the 2-position of the phenyl group. The(meth)acryloyl-containing group may be present at from 4- to 8-positionof the benzotriazole ring, and is preferably present at from 3- to6-position of the phenyl group. Further, at least two(meth)acryloyl-containing groups may be present, and preferably one(meth)acryloyl-containing group is present.

At 4- to 8-positions of the benzotrizole ring and at 3- to 6-positionsof the phenyl group, where no (meth)acryloyl-containing group ispresent, at least one substituent may be present, and such a substituentis preferably a hydrocarbon group such as an alkyl group, a hydroxygroup, an alkoxy group or a halogen atom. The number of carbon atoms inthe hydrocarbon group or the alkoxy group is preferably at most 6.

The (meth)acryloyl-containing group is preferably a (meth)acryloyloxygroup or an organic group represented by the above formula (1). Morepreferred as the (meth)acryloyl-containing group is a (meth)acryloyloxygroup, a (meth)acryloyloxyalkyl group or a ((meth)acryloyloxy)alkoxygroup, as mentioned above, and the number of carbon atoms at a moietyother than the (meth)acryloyloxy group moiety in the latter two groupsis preferably from 2 to 4.

Preferred as the polymerizable benzotriazole compound is a2-(2-hydroxyphenyl)benzotriazole having a (meth)acryloyl-containinggroup at the 5-position of the 2-hydroxyphenyl group. This compound isrepresented by the following formula (3). In the following formula (3),A is the above-mentioned (meth)acryloyl-containing group, and each of R⁴and R⁵ is a substituent other than the (meth)acryloyl-containing group.

As specific examples of the polymerizable benzotriazole compound, thefollowing compounds may be mentioned.

2-{2-Hydroxy-5-((meth)acryloyloxy)phenyl}benzotriazole,2-{2-hydroxy-3-methyl-5-((meth)acryloyloxy)phenyl}benzotriazole,2-{2-hydroxy-3-t-butyl-5-((meth)acryloyloxy)phenyl}benzotriazole,2-{2-hydroxy-5-(2-(meth)acryloyloxyethyl)phenyl}benzotriazole,2-{2-hydroxy-5-(3-(meth)acryloyloxypropyl)phenyl}benzotriazole, and2-{2-hydroxy-3-t-butyl-5-(2-(meth)acryloyloxyethyl)phenyl}benzotriazole.

2-{2-Hydroxy-3-t-butyl-5-(3-(meth)acryloyloxypropyl)phenyl}benzotriazole,2-{2-hydroxy-3-methyl-5-(2-(meth)acryloyloxyethyl)phenyl}benzotriazole,2-{2-hydroxy-3-methyl-5-(3-(meth)acryloyloxypropyl)phenyl}benzotriazole,2-{2-hydroxy-5-(2-(meth)acryloyloxyethyl)phenyl}-5-chlorobenzotriazole,2-{2-hydroxy-5-(2-(meth)acryloyloxyethyl)phenyl}-5-methylbenzotriazole,2-{2-hydroxy-5-(2-(2-(meth)acryloyloxyethoxycarbonyl)ethyl)phenyl}benzotriazole,2-{2-hydroxy-5-(2-(meth)acryloyloxyethoxy)phenyl}benzotriazole, and2-{2-hydroxy-5-(2-(meth)acryloyloxypropoxy)phenyl}benzotriazole.

As the ultraviolet absorber (b-2), a commercially available knownultraviolet absorber may be used. Such an ultraviolet absorber may, forexample, be a benzotriazole type ultraviolet absorber, a benzophenonetype ultraviolet absorber, a salicylic acid type ultraviolet absorber ora phenyl triazine type ultraviolet absorber. Specifically, for example,the following compounds may be mentioned.

Octyl 3-{3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl}propionate,2-(3,5-di-t-pentyl-2-hydroxyphenyl)benzotriazole,2-(2-hydroxy-5-methylphenyl)benzotriazole,2-(2-hydroxy-3,5-di-t-butylphenyl)benzotriazole,2-(2-hydroxy-3-t-butyl-5-methylphenyl)-5-chlorobenzotriazole,2-(2-hydroxy-3,5-di-t-butylphenyl)-5-chlorobenzotriazole,2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2,2′-dihydroxy-4-methoxybenzophenone, and p-t-butylphenyl salicylate.

The photopolymerization initiator (C) may, for example, be an arylketone type photopolymerization initiator (such as an acetophenone, abenzophenone, an alkylaminobenzophenone, a benzyl, a benzoin, a benzoinether, a benzyldimethylketal, a benzoyl benzoate or an α-acyloximeester), a sulfur-containing photopolymerization initiator (such as asulfide or a thiaxanthone), an acylphosphine oxide (such asacyldiarylphosphine oxide) or another photopolymerization initiator.Such photopolymerization initiators may be used in combination of two ormore. Further, the photopolymerization initiator may be used incombination with a photosensitizer such as an amine. As specificexamples of the photopolymerization initiator, the following compoundsmay be mentioned.

4-Phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone,4-t-butyl-trichloroacetophenone, diethoxyacetophenone,2-hydroxy-2-methyl-1-phenylpropan-1-one,1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one,1-(4-dodecylphenyl)-2-methylpropan-1-one,1-{4-(2-hydroxyethoxy)phenyl}-2-hydroxy-2-methyl-propan-1-one,1-hydroxycyclohexyl phenyl ketone,2-methyl-1-{4-(methylthio)phenyl}-2-morpholinopropan-1-one.

Benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoinisopropyl ether, benzoin isobutyl ether, benzyldimethylketal,benzophenone, benzoyl benzoate, methyl benzoyl benzoate,4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone,3,3′-dimethyl-4-methoxybenzophenone,3,3′,4,4′-tetrakis(t-butylperoxycarbonyl)benzophenone,9,10-phenanthrenequinone, camphorquinone, dibenzosuberone,2-ethylanthraquinone, 4′,4″-diethylisophthalophenone, α-acyloxime esterand methyl phenyl glyoxylate.

4-Benzoyl-4′-methyl diphenyl sulfide, thioxanthone,2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone,isopropylthioxanthone, 2,4-dichlorothioxanthone,2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and2,4,6-trimethylbenzoyl diphenylphosphine oxide.

The amount of use of such a photopolymerization initiator (C) ispreferably from 0.1 to 20 parts by mass per 100 parts by mass of themonomer (A).

In the composition for forming an insulating layer, as the caserequires, a stabilizer such as an antioxidant, a photostabilizer or athermal polymerization inhibitor, a leveling agent, a defoaming agent, athickener, an anti-settling agent, a pigment dispersant, an anti-foggingagent, a fluorinated surfactant, silicone surfactant or hydrocarbonsurfactant for surface tension adjustment, a near infrared absorber,etc. may suitably be incorporated.

In the composition for forming an insulating layer, further, colloidalsilica (D) may be incorporated for the purpose of further improving theabrasion resistance of the obtainable cured coating film. The colloidalsilica (D) is ultrafine particles of silicic anhydride dispersed in adispersion medium comprising water, methanol or the like to form acolloidal dispersion. The average particle size of the colloidal silica(D) is usually at a level of from 1 to 1,000 nm and is not particularlylimited, and is preferably from 1 to 200 nm, particularly preferablyfrom 1 to 50 nm.

Further, the colloidal silica (D) may be one having the particle surfacemodified with a hydrolyzate of a hydrolyzable silane compound so as toimprove the dispersion stability, i.e. one wherein a hydrolyzate of asilane compound is held by some or all of silanol groups on the surfaceof the colloidal silica particles, whereby the surface properties aremodified.

In a case where the colloidal silica (D) is incorporated in thecomposition (i) for forming an insulating layer, its amount (solidcontent) is preferably at most 500 parts by mass, particularlypreferably at most 300 parts by mass per 100 parts by mass of themonomer (A). In a case where the colloidal silica (D) is incorporated,by incorporating it in an amount of at least 0.1 part by mass per 100parts by mass of the monomer (A), effects by its incorporation will beobtained.

Further, it is also preferred to incorporate a photostabilizer so as toimprove the stability against light other than the ultraviolet absorber(B). The photostabilizer is preferably a hindered amine typephotostabilizer, particularly a hindered amine type photostabilizerhaving a 2,2,6,6-tetramethylpiperidine residue. Specifically, forexample, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, or2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonatebis(1,2,2,6,6-pentamethyl-4-piperidyl) may be mentioned. In a case wheresuch a photostabilizer is incorporated, its amount is preferably at most10 parts by mass, particularly preferably at most 5 parts by mass per100 parts by mass of the monomer (A).

Further, in order to impart the water repellency to the insulating layer4, a fluorinated polymerizable monomer (e-1) represented by thefollowing formula (4) may be incorporated as a water repellent monomer(E) in the composition for forming an insulating layer.

CH₂═C(R⁶)COOX³R^(f)  (4)

wherein R⁶ is a hydrogen atom, a methyl group or a trifluoromethylgroup, X³ is a C₁₋₆ bivalent organic group, and R^(f) is a C₄₋₆perfluoroalkyl group.

As examples of the fluorinated polymerizable monomer (e-1) representedby the formula (4), the following may be mentioned.

CH₂═C(R⁶)COOR⁷R^(f)

CH₂═C(R)COOR⁷NR⁸SO₂R^(f)

CH₂═C(R⁶)COOR⁷NR⁸COR^(f)

CH₂═C(R⁶)COOCH₂CH(OH)R⁹R^(f)

wherein R⁷ is a C₁₋₆ alkylene group, R⁸ is a hydrogen atom or a C₁ alkylgroup, and R⁹ is a single bond or a C₁ alkylene group.

In the above formula (4), X³ is preferably a C₂₋₄ alkylene group in viewof availability.

As specific examples of the fluorinated polymerizable monomer (e-1)represented by the above formula (4), perfluorohexylethyl (meth)acrylateand perfluorobutylethyl (meth)acrylate may be mentioned.

The monomers represented by the above formula (4) may be used alone orin combination of two or more.

By R^(f) being a C₄₋₆ perfluoroalkyl group, the fluorinatedpolymerizable monomer (e-1) is compatible with other components such asthe polymerizable monomer (A), and when a coating film of thecomposition (i) for forming an insulating layer is cured, the polymerswill not coagulate with each other. Thus, the obtainable insulatinglayer 4 as a cured product will not become cloudy but have a favorableouter appearance, and the adhesion between the insulating layer 4 andits underlayer (for example, the high resistance layer 3) will be high.When R^(f) is a perfluoroalkyl group having at least 4 carbon atoms, thewater repellency of the insulating layer 4 will be favorable. On theother hand, when R^(f) is a perfluoroalkyl group having at most 6 carbonatoms, when the coating film is cured, the obtainable insulating layer 4as a cured product will not become cloudy, and the adhesion between theinsulating layer 4 and its underlayer (for example, the high resistancelayer 3) will be favorable.

Further, in the composition (i) for forming an insulating layer, anorganic solvent may be incorporated for the purpose of improving thecoating properties of the coating film, or adhesion to the underlayersuch as the high resistance layer 3. The organic solvent is notparticularly limited so long as it has no problem with solubility of themonomer (A), the ultraviolet absorber (B) and other additives, and anyorganic solvent which satisfies the above performance may be used.Further, at least two organic solvents may be used in combination. Theamount of the organic solvent is properly at most 100 times by mass,particularly at most 50 times by mass, relative to the monomer (A).

The organic solvent may, for example, be an organic solvent such as alower alcohol, a ketone, an ether or a cellosolve. In addition, an estersuch as n-butyl acetate or diethylene glycol monoacetate, a haloganatedhydrocarbon, a hydrocarbon or the like may also be used.

The insulating layer 4 made of a cured product of the ultravioletcurable composition (i) for forming an insulating layer may be formed byapplying the composition (i) for forming an insulating layer containingthe above components on a stack having the high resistance layer 3 by aspin coating method, a dip coating method, a flow coating method, aspray coating method, a bar coating method, a gravure coating method, aroll coating method, a blade coating method or an air knife coatingmethod, followed by drying in the case of a composition containing anorganic solvent, and then irradiating the resulting film withultraviolet light for curing.

For example, in a case where the composition for forming an insulatinglayer is applied by a spin coating method, the composition (i) forforming an insulating layer is dropped on a stack having the highresistance layer 3, and a stage on which the stack is placed and fixedis rotated at a predetermined number of revolutions, whereby a uniformthin film of the composition (i) for forming an insulating layer can beformed on the stack.

Specifically, for example, in a case where the amount of the composition(i) for forming an insulating layer dropped on the stack having the highresistance layer 3 is about 1 cm³, it is preferred that the stage onwhich the stack is placed is rotated at an initial number of revolutionsof from 100 to 300 rpm for from about 10 to about 15 seconds, and thenrotated at a maximum number of revolutions of from 1,500 to 2,500 rpmfor from about 0.1 to about 1.0 second.

In a case where the composition (i) for forming an insulating layercontains an organic solvent, the stack after coating film formation ispreferably maintained for example at a temperature range of from 100 to150° C. for about 10 minutes to remove the organic solvent.

The ultraviolet light source may, for example, be a xenon lamp, a lowpressure mercury lamp, a high pressure mercury lamp, an ultrahighpressure mercury lamp, a metal halide lamp, a carbon arc lamp or atungsten lamp.

The irradiation time and the irradiation intensity with ultravioletlight may be properly changed depending upon conditions such as the typeof the monomer (A), the type of the ultraviolet absorber (B), the typeof the photopolymerization initiator (C), the coating film thickness andthe ultraviolet light source. Usually, irradiation for from about 1 toabout 60 seconds is sufficient. Further, for the purpose of completingthe curing reaction, heat treatment may be carried out after theirradiation with ultraviolet light.

The irradiation time and the irradiation intensity with ultravioletlight are preferably properly adjusted so that the energy integratedvalue is from about 500 to about 2,000 mJ/cm² and the peak value of theirradiation intensity becomes from 100 to 500 mW/cm².

in a case where the above ultraviolet curable composition (i) forforming an insulating layer is applied on the high resistance layer 3comprising an inorganic oxide and cured to form the insulating layer 4,the composition (i) for forming an insulating layer is appliedpreferably after a surface treatment (hereinafter referred to asadhesion treatment) to increase the adhesion to the resin component isapplied to the upper surface of the high resistance layer 3, in order toincrease the adhesion between the high resistance layer 3 and theinsulating layer 4.

For the surface treatment for improving the adhesion, for example, thefollowing silane coupling agent may be used.

For example, 3-aminopropyltrimethoxysilane,3-aminopropylmethyldimethoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane,N-(2-aminoethyl)-3-aminopropyltrimethoxysilane,3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane,3-glycidoxypropylmethyldiethoxysilane,3-methacryloxypropylmethyldimethoxysilane,3-methacryloxypropyltrimethoxysilane and3-acryloxypropyltrimethoxysilane may be mentioned as the silane couplingagent to be used for the surface treatment.

The adhesion treatment may be carried out by applying a compositionhaving the above silane coupling agent mixed with an organic solventsuch as a lower alcohol, a ketone, an ether or a cellosolve to the uppersurface of the high resistance layer 3 by e.g. a spin coating method, adip coating method, a flow coating method, a spray coating method, a barcoating method, a gravure coating method, a roll coating method, a bladecoating method or an air knife coating method, followed by drying.

For example, in a case where the adhesion treatment on the upper surfaceof the high resistance layer 3 is carried out by employing a spincoating method, a composition containing the above-described silanecoupling agent is dropped on a stack having the high resistance layer 3,and a stage on which the stack is placed and fixed is rotated at apredetermined number of revolutions to form a thin film of thecomposition containing the silane coupling agent on the upper surface ofthe stack, whereby the adhesion treatment is conducted.

Specifically, in a case where the amount of the composition containingthe silane coupling agent dropped on the upper surface of the highresistance layer 3 is about 1 cm³, the stage on which the stack isplaced is rotated preferably at an initial number of revolutions of from500 rpm to 1,500 rpm for from about 5 to about 15 seconds and then at amaximum number of revolutions of from 1,500 rpm to 2,500 rpm for from0.1 to 1.0 second.

In a case where the composition used for the adhesion treatment containsan organic solvent, the stack after the adhesion treatment is preferablymaintained at from 100 to 150° C. for 30 minutes to remove the organicsolvent.

The thermosetting composition (ii) for forming an insulating layer isnot particularly limited so long as a cured product having lighttransparency is obtainable after heat curing, and it may, for example,be preferably one containing an aqueous/organic solvent dispersion (F)containing solid components comprising colloidal silica (f-1) and apartially condensed product (f-2) of an organoalkoxysilane representedby the following formula (5).

The organoalkoxysilane may, for example, be one represented by thefollowing formula (5):

(R¹⁰)_(a)Si(OR¹¹)_(4-a)  (5)

wherein R¹⁰ is a C₁₋₆ monovalent hydrocarbon group, R¹¹ is a C₁₋₆monovalent hydrocarbon group or a hydrogen atom, and a is an integer offrom 0 to 2.

Each of R¹⁰ and R¹¹ is preferably a C₁₋₄ alkyl group.

The organoalkoxysilane included in the range of the above formula (5) ispreferably methyltrimethoxysilane, methyltrihydroxysilane or a mixturethereof, which may form the partially condensed product (f-2). Inaddition, the organotrialkoxysilane included in the range of the formula(5) may, for example, be tetraethoxysilane, ethyltriethoxysilane,diethyldiethoxysilane, tetramethoxysilane, methyltrimethoxysilane ordimethyldimethoxysilane.

The aqueous/organic solvent dispersion (F) may be one as disclosed inU.S. Pat. No. 3,986,997 by Clark.

Further, other than the above, the aqueous/organic solvent dispersion(F) may, for example, be ones as disclosed in U.S. Pat. Nos. 3,986,997,4,624,870, 4,680,232 and 4,914,143.

The aqueous/organic solvent dispersion (F) may be produced specificallyby adding a trialkoxysilane such as methyltrimethoxysilane to an aqueousdispersion of colloidal silica. Such an aqueous dispersion of colloidalsilica may, for example, be “Ludox HS” (manufactured by DuPont), “Nalco”1034A (manufactured by Nalco Chemical Co.), “OSCAL” (tradename,manufactured by Catalysts & Chemicals Industries Co., Ltd.) or“ORGANOSILICASOL” (tradename, manufactured by Nissan ChemicalIndustries, Ltd.).

The aqueous dispersion of the colloidal silica (f-1) may, for example,be one as disclosed in U.S. Pat. No. 4,177,315 by Ubersax.

The partially condensed product (f-2) of the organoalkoxysilanepreferably contains from about 90 to about 95 mass % of a mixture of theorganoalkoxysilane.

The aqueous/organic solvent dispersion (F) itself (i.e. a combination ofthe colloidal silica (f-1) and the partially condensed product (f-2) ofthe organoalkoxysilane) usually has a solid content of from about 10mass % to about 50 mass %, preferably from about 15 mass % to about 25mass %.

For the thermosetting composition (ii) for forming an insulating layer,an adhesion promoter (G) is preferably mixed with the aqueous/organicsolvent dispersion (F) containing the above organoalkoxysilane andcolloidal silica (f-1) and a sufficient amount of an alcohol, so as toimprove the bonding properties to a substrate to which the compositionis applied.

The adhesion promoter (G) may, for example, be an acrylate ester or amethacrylate ester as disclosed in U.S. Pat. No. 5,411,807. The acrylateester or the methacrylate ester may, for example, be specifically Tonemonomer commercially available from Union Carbide Coating Resins.

As the acrylate ester or the methacrylate ester, for example,caprolactone acrylate or caprolactone methacrylate may suitably be usedas the adhesion promoter (G).

The acrylate ester or the methacrylate ester is used usually in anamount of from about 1 to about 20 parts by mass, preferably from about3 to about 8 parts by mass, per 100 parts by mass of the resin solidcontent.

As the adhesion promoter (G), in addition to the above ones, a polyesterpolyol may be used. As the polyester polyol, for example, a caprolactonetype polyester polyol as disclosed in U.S. Pat. No. 5,349,002 may beused.

Many of caprolactone type polyester polyols are bifunctional ortrifunctional, and for example, Tone polyols commercially available fromUnion Carbide Coating Resins. Specifically, for example, “Tone 0200diol” (tradename, manufactured by Union Carbide Coating Resins), “Tone0301 triol” (tradename, manufactured by Union Carbide Coating Resins) or“Tone 0310 triol” (tradename, manufactured by Union Carbide CoatingResins) may be used.

Further, various commercially available Tone polyols differing in themolecular weight, the hydroxy value, the melting point, the viscosityand the like from the above-mentioned Tone polyols may also be used asthe adhesion promoter (G).

The polyester polyol other than the caprolactone type polyester polyolmay be a urethane-modified polyester polyol or a silicone-modifiedpolyester polyol.

The polyester polyol may be used usually in an amount of from about 1 to10 parts by mass per 100 parts by mass of the resin solid content.

As the adhesion promoter (G), in addition to the above ones, anacrylated polyurethane or a methacrylated polyurethane may be used. Theacrylated polyurethane or the methacrylated polyurethane may, forexample, be ones as disclosed in U.S. Pat. No. 5,503,935. The acrylatedpolyurethane or the methacrylated polyurethane usually has a molecularweight within a range of from about 400 to about 1,500, and is usuallysemi-solid or viscous, and can be directly added to a siliconedispersion.

The acrylated polyurethane may, for example, be specificallycommercially available products such as “Actilane CB-32” (tradename,manufactured by SNPE Chimie (France)) and “Ebecryl 8804” (tradename,manufactured by Radcure Specialties (Louisville, Ky.)). Themethacrylated urethane may, for example, be specifically a commerciallyavailable product such as “M-407” (tradename, manufactured by EchoResins & Laboratory). Here, “M-407” is an adduct of isophoronediisocyanate and 2-hydroxyethyl methacrylate having a molecular weightof about 482.

The acrylated polyurethane or the methacrylate polyurethane may be usedusually in an amount of from about 1 to about 15 parts by mass per 100parts by mass of the resin solid content.

As the adhesion promoter (G), in addition to the above ones, an acryliccopolymer having a (number average) molecular weight of from about 1,000to about 10,000 having a reactive moiety or an interactive moiety may beused. Such an acrylic copolymer (which is usually thermosetting) may,for example, be ones as disclosed in U.S. Pat. No. 5,503,935, which canbe directly added to a silicone dispersion.

The acrylic copolymer has, as the reactive moiety or the interactivemoiety, hydroxy groups, and has a hydroxy value within a range of fromabout 30 to about 160, an acid value less than about 4, and a (numberaverage) molecular weight of from about 1,000 to about 10,000.

The acrylic copolymer may, for example, be ones as disclosed in“Encyclopedia of Polymer Science and Engineering, Mark et al., Vol. 4published by John Wiley & Sons, 1986, at pages 374 to 375”, and they maybe prepared by radical polymerization of various comonomers.

The acrylic copolymer can have appropriate properties in combination, byusing a plurality of monomers, as disclosed in Organic Polymer Chemistryby K. J. Saunders, published by Chapman Hall (London), 1973.

For example, in a case where a monomer such as acrylonitrile or methylmethacrylate is used, usually, hardness is imparted to the obtainablecopolymer, and in a case where a monomer such as ethyl acrylate or2-ethylhexyl acrylate is used, flexibility is imparted to the obtainablecopolymer. Further, by using a monomer such as dimethylaminoethylmethacrylate or acrylic acid, usually a reactive moiety suitable forpolymerization is imparted.

The acrylic copolymer as the adhesion promoter (G) may have an aminogroup, a carboxy group, an amido bond, an epoxy group, a hydroxy groupor an acyloxy group.

As the acrylic copolymer, specifically, an acrylic polyol “Joncryl(trademark)” (tradename, manufactured by BASF) or an acryloid acrylicresin (manufactured by Rohm and Haas Company) may, for example, be usedas the adhesion promoter (G).

As disclosed in U.S. Pat. No. 5,503,935, the acrylic copolymer ispreferably a hydroxyalkyl acrylate type, which has a reactive moiety oran interactive moiety with a silanol. As the acrylic copolymer, oneprepared by a method as disclosed in the article “Journal of CoatingTechnology, Kamath et al., Vol. 59, No. 746 (March, 1987)” at pages 51to 56 may be used as a preferred adhesion promoter (G).

The acrylic copolymer may be used usually in an amount of from about 1to about 15 parts by mass per 100 parts by mass of the resin solidcontent.

For production of the aqueous/organic solvent dispersion (F) forexample, an organic solvent such as a C₁₋₄ alkanol such as methanol,ethanol, propanol, isopropanol or butanol; or a glycol or glycol ethersuch as propylene glycol methyl ether, or a mixture thereof may besuitably used.

In a case where the thermosetting composition (ii) for forming aninsulating layer contains the above aqueous/organic solvent dispersion(F), the composition (ii) for forming an insulating layer preferablycontains the adhesion promoter (G) comprising an acrylic polyol in anamount of from 1 to 10 parts by mass per 100 parts by mass of theaqueous/organic solvent dispersion (F) containing solid componentscomprising from 10 to 70 mass % of the colloidal silica (f-1) and from30 to 90 mass % of the partially condensed product (f-2) of theorganoalkoxysilane represented by the formula (5), in a proportion offrom 10 to 50 mass %.

An ultraviolet absorber (J) to be incorporated in the thermosettingcomposition (ii) for forming an insulating layer is suitably one whichco-reacts with a silane, and which will not substantially volatilizeduring the heat curing step. The ultraviolet absorber (J) may, forexample, be 4[γ-(trimethoxysilyl)propoxy]-2, hydroxybenzophenone,4[γ-(triethoxysilyl)propoxy]-2, hydroxybenzophenone or a mixturethereof. The ultraviolet absorber (J) may be incorporated at aconcentration of from 0.1 to 20 mass % in the thermosetting composition(ii) for forming an insulating layer.

In the thermosetting composition (ii) for forming an insulating layer,another additive such as a free-radical initiator, a sterically hinderedamine type photostabilizer, an antioxidant, a dye, aflowability-improving agent, a leveling agent or a surface lubricant maybe incorporated.

In the thermosetting composition (ii) for forming an insulating layer,to shorten the curing time, as a catalyst, a tetrabutylammoniumcarboxylate catalyst such as tetra-n-butylammonium acetate (TBAA) ortetra-n-butylammonium formate may be incorporated.

The insulating layer 4 made of a cured product of the thermosettingcomposition (ii) for forming an insulating layer may be formed byapplying the above thermosetting composition (ii) for forming aninsulating layer on the upper surface of a stack having the highresistance layer 3 by an optional known coating method such as a spincoating method, a dip coating method, a flow coating method, a spraycoating method, a bar coating method, a gravure coating method, a rollcoating method, a blade coating method or an air knife coating method,and curing the composition by heating at from 100 to 150° C. for fromabout 30 to about 90 minutes or by applying infrared or microwaveenergy.

For example, in a case where the composition (ii) for forming aninsulating layer is applied by employing a spin coating method, thecomposition (ii) for forming an insulating layer is dropped on a stackhaving the high resistance layer 3, and a stage on which the stack isplaced and fixed is rotated at a predetermined number of revolutions,whereby a uniform thin film of the composition (ii) for forming aninsulating layer can be formed on the upper surface of the stack.

Specifically, for example, when the amount of the composition (ii) forforming an insulating layer dropped on the stack having the highresistance layer 3 is about 1 cm³, the stage on which the stacked isplaced and fixed is preferably rotated at an initial number ofrevolutions of from 100 to 300 rpm for from about 10 to about 15 secondsand then at a maximum number of revolutions of from about 1,500 to about2,500 rpm for from 0.1 to 1.0 second.

By the insulating layer 4 being a layer formed by curing the abovecomposition for forming an insulating layer, the rate of formation ofthe insulating layer 4 is increased, whereby the efficiency forproduction of the front panel 1 for a touch sensor can be increased.

In a case where the insulating layer 4 is a layer made of cured productof the composition for forming an insulating layer, its thickness ispreferably at least 1 μm and at most 100 μm, more preferably at least 1μm and at most 30 μm, further preferably at least 1 μm and at most 10μm.

When the thickness of the insulating layer 4 made of a cured product ofthe composition for forming an insulating layer is at least 1 μm,sufficient abrasion resistance and weather resistance of the insulatinglayer 4 can be obtained. On the other hand, when the thickness of theinsulating layer 4 made of a cured product of the composition forforming an insulating layer is at most 100 μm, curing will sufficientlyproceed even at a deep portion of the insulating layer 4, wherebyexcellent light transmittance will be obtained, and in addition,sufficient bending strength of the front panel 1 for a touch sensor canbe obtained.

Further, the insulating layer 4 is not limited to a layer made of acured product of the composition for forming an insulating layer, andmay be a layer containing, as the main component, an inorganic oxidehaving electrical insulating property i.e. the above-described volumeresistivity and having light transmittance.

The insulating layer 4 comprising a layer containing an inorganic oxideas the main component may, for example, be a layer containing siliconoxide as the main component or a layer containing aluminum oxide as themain component. Among them, a layer containing silicon oxide as the maincomponent is suitably used, since it has sufficient abrasion resistanceand weather resistance while maintaining favorable light transmittanceand low reflectance to visible light.

The layer containing silicon oxide as the main component may be a layerconsisting solely of silicon oxide, or a layer containing silicon oxideas the main component and containing at least one member selected fromboron and phosphorus as an added element other than silicon.

The insulating layer 4 comprising a layer containing an inorganic oxideas the main component may be formed on a stack having the highresistance layer 3 by sputtering such as DC (direct current) sputteringsuch as DC (direct current) magnetron sputtering, AC (alternatingcurrent) sputtering or RF (radio-frequency) sputtering, in the samemanner as formation of the high resistance layer 3.

In a case where the insulating layer 4 is a layer containing siliconoxide as the main component, as a target to be used for formation of thehigh resistance layer 3, a target containing silicon as the maincomponent may be used. The target containing silicon as the maincomponent may be one consisting solely of silicon, or may be onecontaining silicon as the main component doped with an element otherthan silicon, for example, a known dopant such as boron or phosphorus,within a range not to impair the effects of the present invention.

Formation of the insulating layer 4 comprising a layer containing aninorganic oxide as the main component by sputtering may be carried outby properly adjusting conditions such as the pressure of the sputteringgas and the film deposition rate, in the same manner as sputtering forthe high resistance layer 3.

Further, formation of the layer containing an inorganic oxideconstituting the insulating layer is not limited to a sputtering method,and may be carried out by a physical vapor deposition method other thanthe sputtering method, such as a vacuum deposition method, an ion beamassisted deposition method or an ion plating method, or a chemical vapordeposition method such as a plasma CVD method.

In a case where the insulating layer 4 is the above layer containing aninorganic oxide, its thickness is preferably at least 50 nm and at most5 μm, more preferably at least 50 nm and at most 1 μm, furtherpreferably at least 50 nm and at most 500 nm.

When the thickness of the insulating layer 4 is at least 50 nm,sufficient abrasion resistance and weather resistance of the insulatinglayer 4 can be obtained. Further, when the thickness of the insulatinglayer 4 is at most 5 μm, the insulating layer 4 has a moderate bendingstrength and further has a sufficient light transmittance. Further, whenthe thickness of the insulating layer 4 is at most 500 nm, the angledependence of the reflected color can be reduced, and excellentvisibility will be obtained.

In the front panel 1 for a touch sensor, the refractive index (n) of theinsulating layer 4 is preferably from 1.3 to 1.8 with a view toobtaining excellent optical properties such as the luminoustransmittance and the luminous reflectance.

In a case where the insulating layer 4 contains no component to impartwater repellency such as the above fluorinated polymerizable monomer(e-1), moisture which is brought into contact with the surface of theinsulating layer 4 is likely to be diffused in and attached to thesurface of the insulating layer 4, whereby the electrostatic attraction(Coulomb force) working between the high resistance layer 3 on which theelectric charge is accumulated and the sensory receptor X such as afingertip close to the surface layer of the insulating layer 4 will beblocked out, and accordingly no sufficient functions as a touch sensormay be obtained. Accordingly, on the upper surface of an insulatinglayer 4 which does not contain a sufficient amount of a component toimpart the water repellency, a water repellent layer 6 is preferablyfurther formed as shown in FIG. 4.

Specifically, for example, a water repellent layer 6 is preferablyformed on the upper surface of the insulating layer 4, in a case wherethe insulating layer 4 is a layer constituted by an insulating materialcontaining an inorganic oxide as the main component, or in a case wherethe insulating layer 4 is a layer made of a cured product of theultraviolet curable composition (i) for forming an insulating layercontaining no component to impart the water repellency such as thefluorinated polymerizable monomer (e-1).

More specifically, it is more preferred to form a water repellent layer6 on the upper surface of the insulating layer 4, for example, when itis a layer containing a silicon oxide as the main component. By such aconstitution, blocking of the electrostatic attraction (Coulomb force)working between the high resistance layer 3 and the sensory receptor X,by moisture in contact with the surface of the insulating layer 4, canbe suppressed, whereby sufficient functions as a touch sensor of thefront panel 1 for a touch sensor can be obtained.

The water repellent layer 6 may be formed by a layer made of a curedproduct of a composition for forming a water repellent layer containinga fluorinated compound or a silicon-containing compound (hereinafterreferred to as a water repellent agent (H)).

The fluorinated compound or the silicon-containing compound constitutingthe water repellent agent (H) may, for example, be a silane couplingagent. The silane coupling agent may be a fluorinated silane couplingagent, a silane coupling agent having an amino group, a silane couplingagent having an acryloyl group, a silane coupling agent having amethacryloyl group, a silane coupling agent having a thiol group, asilane coupling agent having an isocyanate group or a silane couplingagent having an oxiranyl group. Further, commercially available productssuch as FS-10 (manufactured by Shin-Etsu Chemical Co., Ltd.) may also beused.

The silane coupling agent is preferably a fluorinated silane couplingagent in view of the water repellency and the like, particularlypreferably a silane coupling agent having a fluoroalkyl group. Thefluoroalkyl group may, for example, be a perfluoroalkyl group or afluoroalkyl group having a perfluoro(polyoxyalkylene) chain.

A commercially available silane coupling agent having a fluoroalkylgroup may, for example, be AQUAPHOBE (registered trademark) CFmanufactured by Gelest, Inc., Novec (registered trademark) EGC-1720manufactured by Sumitomo 3M Limited, OPTOOL (registered trademark) DSXmanufactured by Daikin Industries, Ltd. (a silane coupling agent havinga perfluoro(polyoxyalkylene) chain).

The silane coupling agent having an amino group may, for example, beaminopropyltriethoxysilane, aminopropylmethyldiethoxysilane,aminoethyl-aminopropyltrimethoxysilane oraminoethyl-aminopropylmethyldimethoxysilane.

The water repellent layer 6 may be formed by applying the compositionfor forming a water repellent layer containing the above water repellentagent to the upper surface of a stack having the insulating layer 4,followed by heat treatment, or by vapor phase deposition of the waterrepellent agent on the upper surface of a stack having the insulatinglayer 4, followed by heat treatment.

In a case where the water repellent layer 6 is formed by applying thecomposition for forming a water repellent layer, the coating method may,for example, be a spin coating method, a dip coating method, a castingmethod, a slit coating method or a spray coating method. The heattreatment temperature is preferably from 20 to 150° C., particularlypreferably from 70 to 140° C. in view of productivity. The humidity maybe controlled at the time of heat treatment so as to increase thereactivity of the water repellent agent.

In a case where the water repellent layer 6 is formed by vapordeposition of the composition for forming a water repellent layer, forexample, the solvent is removed from the composition for forming a waterrepellent layer, the composition is heated to from 250 to 300° C. in avacuum state, a stack having the insulating layer 4 is put in anatmosphere of the water repellent agent (H) in a vapor state, and such astate is maintained for a predetermined time, whereby gas molecules ofthe water repellent agent (H) are attached to the surface of the stack,whereby a uniform thin film of the water repellent agent (H) can beformed on the upper surface of the stack.

The front panel 1 for a touch sensor is not limited to the constitutionsas shown in FIGS. 2 to 4, and it may have a barrier layer 7 interposedbetween the transparent substrate 2 and the high resistance layer 3 asshown in FIG. 5 for example.

By interposing the barrier layer 7 between the transparent substrate 2and the high resistance layer 3, diffusion of the components in thetransparent substrate 2 into the high resistance layer 3 can besuppressed, whereby changes in the properties such as the surfaceresistivity of the high resistance layer 3 can be suppressed. Further,the influences of the surface shape of the transparent substrate 2 suchas a glass substrate over the entire front panel 1 for a touch sensorcan be suppressed, whereby the shape stability as a whole can beattained.

The barrier layer 7 may, for example, be a layer containing siliconoxide as the main component, or a layer containing silicon oxide andindium oxide as the main components. Among them, a layer containingsilicon oxide as the main component is preferred, whereby favorablelight transmittance will easily be secured. Further, among layerscontaining silicon oxide as the main component, a layer which furthercontains nitrogen, for example, a layer containing silicon oxynitride(SiON) is more preferred, whereby excellent light transmittance can beobtained and in addition, an effect of reducing the luminous reflectanceof the front panel 1 for a touch sensor can be obtained.

The barrier layer 7 may be formed on the transparent substrate 2 bysputtering such as DC (direct current) sputtering such as DC (directcurrent) magnetron sputtering, AC (alternating current) sputtering or RF(radio-frequency) sputtering, in the same manner as formation of thehigh resistance layer 3.

In a case where the barrier layer 7 is a layer containing silicon oxideas the main component, the target to be used for formation of thebarrier layer 7 may be a target containing silicon as the maincomponent. The target containing silicon as the main component may beone consisting solely of silicon, or may be one containing silicon asthe main component doped with an element other than silicon, forexample, a known dopant such as boron or phosphorus, within a range notto impair the effects of the present invention.

Formation of the barrier layer 7 by sputtering may be carried out byproperly adjusting the conditions such as the pressure of the sputteringgas and the film deposition rate, in the same manner as sputtering forthe high resistance layer 3.

In a case where a layer containing silicon oxide as the main componentand further containing nitrogen, for example, a layer containing siliconoxynitride (SiON) is formed as the barrier layer 7, such a layer may beformed by using, as the sputtering gas, for example, a mixed gas havingan oxygen gas and an inert gas mixed with a nitrogen gas or with a mixedgas having a nitrogen atom-containing gas such as N₂O, NO, NO₂ or NH₃.

Formation of such a barrier layer 7 comprising an inorganic oxide suchas silicon oxide is not limited to the above sputtering method and maybe carried out by a physical vapor deposition method other than thesputtering method, such as a vacuum deposition method, an ion beamassisted deposition method or an ion plating method, or a chemical vapordeposition method such as a plasma CVD method.

The thickness of the barrier layer 7 is preferably at most 100 nm, morepreferably at most 50 nm, further preferably at most 30 nm. When thethickness of the barrier layer is at most 100 nm, an appropriate bendingstrength and a sufficient light transmittance of the entire front panel1 for a touch sensor will be obtained.

In the front panel 1 for a touch sensor, the refractive index (n) of thebarrier layer 7 is preferably from 1.4 to 2.2 with a view to obtainingexcellent visible light transmittance and visible light reflectance.

The luminous transmittance of the front panel 1 for a touch sensor is atleast 85%. By the luminous transmittance of at least 85%, sufficientvisibility will be obtained. The luminous transmittance of the frontpanel 1 for a touch sensor is more preferably at least 90%.

Further, the luminous reflectance of the front panel 1 for a touchsensor is preferably at most 14%, more preferably at most 2%, furtherpreferably at most 1%.

The static friction coefficient of the front panel 1 for a touch sensoris preferably at most 0.2, more preferably at most 0.15.

Further, the dynamic friction coefficient of the front panel 1 for atouch sensor is preferably at most 0.2, more preferably at most 0.15.

Of the front panel 1 for a touch sensor, the indentation modulusevaluated by a microhardness measurement test is preferably at least 2.5GPa, more preferably at least 3.0 GPa.

Here, “the microhardness measurement test” is a test method to calculatethe hardness from the indentation depth, whereby the indentation modulus(GPa) corresponding to the indentation hardness can be known. Thishardness indicates “the hardness” of the front panel 1 for a touchsensor, i.e. the mechanical strength such as the abrasion resistance.

The water contact angle of the front panel 1 for a touch sensor ispreferably at least 80°, more preferably at least 90°. The water contactangle is measured by a contact angle meter.

Such a front panel 1 for a touch sensor is to be provided in front of atouch panel main body 5 as shown in FIG. 3 for example, and is soconstituted that electricity is applied to transparent electrodes 5 a ofthe touch panel main body 5 from a control unit not shown at a voltageand a frequency controlled in a pattern capable of reproducing thetactile feeling to be expressed, and the electric charge induced on theside of the front panel 1 for a touch sensor is accumulated on the highresistance layer 3, whereby the front panel 1 for a touch sensor ischarged. When a sensory receptor X such as a finger is touched to thesurface of the front panel 1 for a touch sensor in such a charged state,a weak electrostatic force works between them by means of the insulatinglayer 4, which is perceived by the sensory receptor X as the sense oftouch such as the concave-convex touch feeling.

The transparent electrodes 5 a may be provided on the front panel 1 fora touch sensor. That is, the transparent electrodes 5 a may be providedon the opposite side of the transparent substrate 2 in the front panel 1for a touch sensor from a side where the high resistance layer 3 isprovided. By such a constitution, the structure of the entire touchpanel can be simplified, and in addition, the driving voltage can besuppressed to be low, since the distance between the transparentelectrodes 5 a and the high resistance layer 3 tends to be short.

The material constituting the transparent electrodes 5 a may, forexample, be tin-doped indium oxide (ITO), indium/gallium-doped zincoxide (IGZO) or gallium-doped zinc oxide (GZO). Among them, ITO ispreferred, in view of favorable transmittance, resistance stability anddurability. The thickness of the transparent electrodes 5 a ispreferably from 50 to 500 nm, more preferably from 100 to 300 nm. Whenthe thickness is at least 50 nm, a sufficient resistance will beobtained and in addition, the stability of the resistance can besecured. When it is at most 500 nm, a sufficient transmittance can besecured.

In a case where the transparent electrodes 5 a are provided on the frontpanel 1 for a touch sensor, the transparent electrodes 5 a are formed byforming a film of a material forming the transparent electrodes 5 a onthe surface of the transparent substrate 2 opposite to the surface wherethe high resistance layer 3 is to be provided e.g. by a sputteringmethod or a deposition method, and forming the film into a pattern of adesired shape e.g. by photolithography or laser patterning.

According to such a front panel 1 for a touch sensor, the surfaceresistivity of the high resistance layer 3 is from 1 to 100 MΩ/□,whereby the desired sense of touch can be developed with goodreproducibility without electrical interaction between the highresistance layer 3 and the transparent electrodes 5 a provided on thetouch panel main body 5, and thus an excellent touch sensor accuracywill be obtained and in addition, a luminous transmittance of at least85% will be obtained, whereby excellent visibility will be obtained.

Now, the present invention will be described in detail with reference toExamples. However, it should be understood that the present invention isby no means restricted to such specific Examples.

Examples 1 to 9 are Examples of the present invention, and Example 10 isa Comparative Example.

<Preparation of Composition for Forming Insulating Layer>

(Preparation of Ultraviolet Curable Resin a1)

Into a 300 mL four-necked flask equipped with a stirrer, 163 g of butylacetate first grade (manufactured by JUNSEI CHEMICAL CO., LTD.) and 41 gof 2-propanol were put, and 2 g of a reactive ultraviolet absorber(manufactured by Otsuka Chemical Co., Ltd., tradename: R-UVA93), 1 g ofa photostabilizer (manufactured by BASF, tradename: TINUVIN292), 0.65 gof a leveling agent (manufactured by BYK Japan K.K., tradename: BYK306),2.5 g of a photopolymerization initiator (manufactured by BASF,tradename: Irgacure907) and 0.1 g of a polymerization inhibitorhydroquinone monomethyl ether (manufactured by JUNSEI CHEMICAL CO.,LTD.) were added thereto and dissolved.

Then, to this solution, 40 g of a multifunctional acrylate (manufacturedby Shin-Nakamura Chemical Co., Ltd., tradename: U15HA), 60 g of apolyfunctional acrylate (manufactured by TOAGOSEI CO., LTD., tradename:M325) and 33 g of an acrylic resin (manufactured by MITSUBISHI RAYONCO., LTD., tradename: LR248) were added, stirred and dissolved at roomtemperature until the solution became uniform, thereby to obtain anultraviolet curable resin a1 which is a composition for forming aninsulating layer.

(Preparation of Ultraviolet Curable Resin a2)

Into a 300 mL four-necked flask equipped with a stirrer, 163 g of butylacetate first grade (manufactured by JUNSEI CHEMICAL CO., LTD.) and 41 gof 2-propanol were put, and 2 g of a reactive ultraviolet absorber(manufactured by Otsuka Chemical Co., Ltd., tradename: R-UVA93), 1 g ofa photostabilizer (manufactured by BASF, tradename: TINUVIN292), 0.65 gof a leveling agent (manufactured by BYK Japan K.K., tradename: BYK306),2.5 g of a photopolymerization initiator (manufactured by BASF,tradename: Irgacure907) and 0.1 g of a polymerization inhibitorhydroquinone monomethyl ether (manufactured by JUNSEI CHEMICAL CO.,LTD.) were added thereto and dissolved.

Then, to this solution, 60 g of a multifunctional acrylate (manufacturedby Shin-Nakamura Chemical Co., Ltd., tradename: U15HA), 40 g of apolyfunctional acrylate (manufactured by TOAGOSEI CO., LTD., tradename:M325), 1 g of a fluorinated acrylate (manufactured by Asahi GlassCompany, Limited, tradename: C6FMA) and 17 g of an acrylic resin(manufactured by MITSUBISHI RAYON CO., LTD., tradename: LR248) wereadded, stirred and dissolved at room temperature until the solutionbecame uniform, thereby to obtain an ultraviolet curable resin a2 whichis a composition for forming an insulating layer.

(Preparation of Ultraviolet Curable Resin a3)

Into a 300 mL four-necked flask equipped with a stirrer, 122 g of butylacetate first grade (manufactured by JUNSEI CHEMICAL CO., LTD.) and 31 gof 2-propanol were put, and 0.65 g of a fluorinated surfactant(manufactured by AGC Seimi Chemical Co., Ltd., tradename: Surflon S420)and 2.5 g of a photopolymerization initiator (manufactured by BASF,tradename: Irgacure907) were added thereto and dissolved.

Then, to this solution, 150 g of a multifunctional acrylate(manufactured by Shin-Nakamura Chemical Co., Ltd., tradename: A-DPH) wasadded, stirred and dissolved at room temperature until the solutionbecame uniform, thereby to obtain an ultraviolet curable resin a3 whichis a composition for forming an insulating layer.

(Thermosetting Resin b1)

As a thermosetting composition for forming an insulating layer, athermosetting silicone hard coating agent (manufactured by MomentivePerformance Materials Inc., tradename: PHC587C) was used. Hereinafter,this silicone hard coating agent will be referred to as a thermosettingresin b1.

Example 1

A glass substrate Q1 (manufactured by Asahi Glass Company, Limited,tradename: AS glass, 100 mm×100 mm×1 mm in thickness) was put in avacuum chamber, and the vacuum chamber was evacuated until the pressurein the chamber became 1×10⁻⁴ Pa. Then, a film formation treatment wasconducted on the glass substrate Q1 under the following conditions toform a high resistance layer A1.

That is, while a mixed gas having 2 vol % of an oxygen gas mixed with anargon gas was introduced, co-sputtering was carried out by a magnetronsputtering method under a pressure of 0.1 Pa using a tin oxide target(manufactured by AGC CERAMICS CO., LTD., tradename: GIT target) and atitanium oxide target (manufactured by AGC CERAMICS CO., LTD.,tradename: TXO target).

With the GIT target, pulse sputtering was carried out under conditionsof a frequency of 20 kHz, a power density of 3 W/cm² and a reverse pulsewidth of 5 μsec, and with the TXO target, pulse sputtering was conductedunder conditions of a frequency of 20 kHz, a power density of 4 W/cm²and a reverse pulse width of 5 μsec. As a result, a high resistancelayer A1 having a thickness of 20 nm was formed on the surface of theglass substrate Q1.

The atomic composition of the high resistance layer A1 was analyzed byESCA (manufactured by Physical Electronics, Inc., tradename: QuanteraSXM) and as a result, the atomic ratio was Sn:Ti=9:1.

Then, on the high resistance layer A1, an adhesion treatment wasconducted by the following method.

First, 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-EtsuChemical Co., Ltd., tradename: KBM503) was diluted to 0.1 mass % withethanol, about 1 cm³ of the diluted liquid was dropped on the surface ofthe high resistance layer A1, and the stack was rotated at a number ofrevolutions of 1,000 rpm for 10 seconds and then at 2,000 rpm for 0.5second by a spin coater for coating. Then, the stack was put in aconstant temperature chamber and maintained at 120° C. for 30 minuets.In such a manner, an adhesion treatment was conducted on the highresistance layer A1.

Then, an insulating layer B1 was formed by the following method.

First, about 1 cm³ of the ultraviolet curable resin a1 was dropped onthe surface subjected to the adhesion treatment of the high resistancelayer A1, and then the stack was rotated at a number of revolutions of200 rpm for 10 second and then at 2,000 rpm for 0.5 second by a spincoater to form a coating film. Then, the stack was put and maintained at120° C. for 10 minutes to dry the coating film.

Then, the stack having a dried coating film formed thereon wasirradiated with ultraviolet light by using an UV irradiation apparatusprovided with a conveyor (manufactured by USHIO INC., apparatus name:UVC-02516S1) while the transfer rate and the UV intensity were adjustedso that the UV irradiation integrated value became 1,000 mJ/cm² and thepeak value became 375 mW/cm², to cure the coating film, thereby to forman insulating layer B1 made of a cured product of the ultravioletcurable resin a1. The thickness of the insulating layer B1 was 10 μm.

In such a manner, a front panel 1 for a touch sensor comprising the highresistance layer A1 and the insulating layer B1 stacked on the glasssubstrate Q1 was obtained.

Example 2

In the same manner as in Example 1 except that the ultraviolet curableresin a2 was used instead of the ultraviolet curable resin a1 as thecomposition for forming an insulating layer, a front panel 2 for a touchsensor comprising a high resistance layer A1 having a thickness of 20 nmand an insulating layer B2 having a thickness of 10 μm stacked on theglass substrate Q1 was obtained.

Example 3

In the same manner as in Example 1, a high resistance layer A1 wasformed on the glass substrate Q1. On the high resistance layer A1,without an adhesion treatment, an insulating layer B3 was formed asfollows.

That is, about 1 cm³ of the thermosetting resin b1 was dropped on thehigh resistance layer A1, and the stack was rotated at a number ofrevolutions of 200 rpm for 10 seconds and then at 2,000 rpm for 0.5second by a spin coater, and then put in a constant temperature chamberand maintained at 120° C. for 60 seconds to thermally cure thethermosetting resin b1, thereby to form an insulating layer B3. Thethickness of the insulating layer B3 was 5 μm.

In such a manner, a front panel 3 for a touch sensor comprising the highresistance layer A1 and the insulating layer B3 stacked on the glasssubstrate Q1 was obtained.

Example 4

The glass substrate Q1 was put in a vacuum chamber, and the vacuumchamber was evacuated until the pressure in the chamber became 1×10⁻⁴Pa. Then, a film deposition treatment was carried out on the glasssubstrate Q1 by a magnetron sputtering method under the followingconditions to form a barrier layer Ca and a high resistance layer A1 inorder.

First, while a mixed gas having 40 vol % of an oxygen gas mixed with anargon gas was introduced, pulse sputtering was carried out by using a Sitarget under conditions of a pressure of 0.3 Pa, a frequency of 20 kHz,a power density of 3.8 W/cm² and a reverse pulse width of 5 μsec, toform a barrier layer C1 having a thickness of 20 nm comprising siliconoxide on the surface of the glass substrate Q1.

Then, on the barrier layer C1, in the same manner as in Example 1, ahigh resistance layer A1 having a thickness of 20 nm was formed. In sucha manner, by a magnetron sputtering method, a stack comprising thebarrier layer C1 and the high resistance layer A1 stacked on the glasssubstrate Q1 was obtained.

Then, an adhesion treatment was conducted on the high resistance layerA1 of the stack thus obtained in the same manner as in Example 1, andthen an insulating layer B2 having a thickness of 10 μm was formed inthe same manner as in Example 2 to obtain a front panel 4 for a touchsensor.

Example 5

In the same manner as in Example 4 except that the ultraviolet curableresin a3 was used instead of the ultraviolet curable resin a1 as thecomposition for forming an insulating layer, and that the stack wasrotated at a number of revolutions of 300 rpm for 10 seconds and then at2,000 rpm for 0.5 second by a spin coater to form an insulating layer, afront panel 5 for a touch sensor comprising a high resistance layer A1having a thickness of 20 nm and an insulating layer B5 having athickness of 10 μm stacked on the glass substrate Q1 was obtained.

Example 6

On the glass substrate Q1, in the same manner as in Example 4, a barrierlayer C1 having a thickness of 20 nm was formed. Then, in the samemanner as in Example 1 except that the power density in the pulsesputtering by the GIT target was changed from 3 W/cm² to 3.8 W/cm²,co-sputtering was carried out by a magnetron sputtering method. In sucha manner, a high resistance layer A2 having a thickness of 20 nm wasformed on the barrier layer C1.

The atomic composition of the high resistance layer A2 was analyzed byESCA (Physical Electronics, Inc., apparatus name: Quantera SXM) and as aresult, the atomic ratio was Sn:Ti=9:1.

Then, while a mixed gas having 40 vol % of an oxygen gas mixed with anargon gas was introduced, pulse sputtering was carried out by amagnetron sputtering method using a Si target under conditions of apressure of 0.3 Pa, a frequency of 20 kHz, a power density of 3.8 W/cm²and a reverse pulse width of 5 μsec to form an insulating layer B4having a thickness of 100 nm comprising silicon oxide on the highresistance layer A2.

Then, on the insulating layer B4, a water repellent layer D1 was formedby the following method. First, in a crucible as a heating container, 75g of OPTOOL (registered trademark) DSX (manufactured by DaikinIndustries, Ltd.) as a deposition material was put, and the crucible wasevacuated by a vacuum pump for at least 10 hours to remove the solvent.

Then, the crucible was heated in the vacuum chamber until thetemperature in the crucible reached 270° C. and further maintained forabout 10 minutes until the temperature in the crucible was stabilized,and then the stacked substrate comprising the barrier layer C1, the highresistance layer A2 and the insulating layer B4 formed in this order onthe glass substrate Q1 was introduced into the vacuum chamber to carryout film formation. In such a manner, a water repellent layer D1 havinga thickness of 15 nm was formed on the insulating layer B4, thereby toobtain a front panel 6 for a touch sensor.

Example 7

The glass substrate Q1 was put in a vacuum chamber, the vacuum chamberwas evacuated until the pressure in the chamber became 1×10⁻⁴ Pa, andthen a film formation treatment was conducted on the glass substrate Q1by a magnetron sputtering method under the following conditions to forma barrier layer C2 and a high resistance layer A3 in order.

First, while a mixed gas having 5 vol % of an oxygen gas mixed with anargon gas was introduced, pulse sputtering was carried out by using atarget having 30 mass % of silicon oxide mixed with indium oxide, underconditions of a pressure of 0.3 Pa, a frequency of 20 kHz, a powerdensity of 3.8 W/cm² and a reverse pulse width of 5 μsec, to form abarrier layer C2 having a thickness of 70 nm on the surface of the glasssubstrate Q1.

Then, co-sputtering was carried out by a magnetron sputtering method inthe same manner as in Example 1 except that the gas to be introducedinto the vacuum chamber was changed from the mixed gas having 2 vol % ofan oxygen gas mixed with an argon gas to a mixed gas having 5 vol % ofan oxygen gas mixed with an argon gas, and that the power density in thepulse sputtering using the GIT target was changed from 3 W/cm² to 3.8W/cm². In such a manner, a high resistance layer A3 having a thicknessof 100 nm was formed on the barrier layer C2.

The atomic composition of this high resistance layer A3 was analyzed byESCA (manufactured by Physical Electronics Inc., apparatus name:Quantera SXM) and as a result, the atomic ratio was Sn:Ti=93:7.

Then, on the high resistance layer A3, in the same manner as in Example5, an insulating layer B4 having a thickness of 90 nm comprising siliconoxide was formed, and on the insulating layer B4, a water repellentlayer D1 having a thickness of 15 nm was formed in the same manner as inExample 6. In such a manner, a front panel 8 for a touch sensorcomprising the barrier layer C2, the high resistance layer A3, theinsulating layer B4 and the water repellent layer D1 stacked in thisorder on the glass substrate Q1 was obtained.

Example 8

In the same manner as in Example 6 except that the thickness of theinsulating layer was 1 μm, a barrier layer C1 having a thickness of 20nm, a high resistance layer A2 having a thickness of 20 nm, aninsulating layer B4 having a thickness of 1 μm and a water repellentlayer D1 having a thickness of 15 nm were stacked in this order on theglass substrate Q1 to obtain a front panel 8 for a touch sensor.

Example 9

In the same manner as in Example 4 except that a glass substrate Q2 (100mm×100 mm×0.8 mm in thickness) obtained by subjecting aluminasilicateglass to a chemical tempering treatment was used instead of the glasssubstrate Q1, a front panel 9 for a touch sensor was obtained.

The glass material for the glass substrate Q2 has a compositioncomprising, as represented by mol %, 64.5% of SiO₂, 8% of Al₂O₃, 12.5%of Na₂O, 4% of K₂O, 10.5% of MgO, 0.1% of CaO, 0.1% of SrO, 0.1% of BaOand 0.5% of ZrO₂. The chemical tempering treatment was carried out byimmersing a glass plate of aluminasilicate glass having the abovecomposition in a KNO₃ molten salt to carry out ion exchange treatmentand then cooling the glass plate to the vicinity of room temperature. Ofthe obtained tempered glass, the surface compressive stress was 735 MPa,and the thickness of the compressive stress layer was 51.2 μm. Thesurface compressive stress and the thickness of the compressive stresslayer were measured by a surface compressive stress meter FSM-6000(manufactured by Orihara Manufacturing Co., Ltd.).

Example 10

In the same manner as in Example 6 except that the glass substrate Q2was used instead of the glass substrate Q1, a front panel 10 for a touchsensor was obtained.

Example 11

On the glass substrate Q1, in the same manner as in Example 4, a barrierlayer C1 having a thickness of 20 nm was formed.

Then, while a mixed gas having 2 vol % of an oxygen gas mixed with anargon gas was introduced, pulse sputtering was carried out by amagnetron sputtering method by using a target having 50 mass % of indiumoxide mixed with gallium oxide (manufactured by Sumitomo Metal MiningCo., Ltd., tradename: GIO target) under conditions of a pressure of 0.1Pa, a frequency of 20 kHz, a power density of 0.8 W/cm² and a reversepulse width of 5 μsec. As a result, a high resistance layer A4 having athickness of 15 nm was formed on the surface of the barrier layer C1.

The atomic composition of the high resistance layer A4 was analyzed byESCA (manufactured by Physical Electronics, Inc., apparatus name:Quantera SXM) and as a result, the atomic ratio was Ga:In=6:4.

Then, on the high resistance layer A4, an adhesion treatment wasconducted in the same manner as in Example 1, and then an insulatinglayer B1 made of a cured 3 o product of the ultraviolet curable resin a1was formed in the same manner as in Example 1, to obtain a front panel11 for a touch sensor.

Of the front panels 1 to 11 for a touch sensor obtained in Examples 1 to11, the luminous transmittance, the luminous reflectance, the surfaceresistivity of the high resistance layer, the indentation modulus, theangle dependence of the reflected color, the static frictioncoefficient, the dynamic friction coefficient, the water contact angleand the sensitivity of the touch sensor were measured respectively bythe following methods. The constitution of the respective layers of thefront panels 1 to 11 for a touch sensor is shown in Table 1, and themeasurement results are shown in Table 2.

(Luminous Transmittance)

The spectral transmittance of the front panel for a touch sensor wasmeasured by a spectrophotometer (manufactured by Shimadzu Corporation,apparatus name: SolidSpec-3700), and from the spectral transmittance,the stimulus value Y as specified by JIS Z8701 was calculated, which wasregarded as the luminous transmittance.

(Luminous Reflectance)

The reflectance of the front panel for a touch sensor was measured by aspectrophotometer (manufactured by Shimadzu Corporation, model:UV3150PC), and from the reflectance, the luminous reflectance (thestimulus value Y of reflection as specified by JIS Z8701) was obtained.In order to cancel out the back (side) reflection of the front panel,the rear side of the glass substrate was painted in black to carry outmeasurement.

(Surface Resistivity)

After the high resistance layer was formed, the surface resistivity ofthe high resistance layer was measured by a measuring apparatus(manufactured by Mitsubishi Chemical Analytech Co., Ltd., apparatusname: Hiresta UP (MCP-HT450 model)). A probe was applied to the centerof the 10 cm square front panel and electricity was applied at 10 V for10 seconds for measurement.

(Indentation Modulus)

The indentation modulus (GPa) of the front panel for a touch sensor wasmeasured by using a microhardness testing machine (manufactured byFischer Instruments, apparatus name: PICODENTOR HM500) in accordancewith ISO14577. For measurement, a Vickers indenter was used.

(Angle Dependence of Reflected Color)

The rear side of the glass substrate was painted in black to cancel outthe back (side) reflection of the front panel, and such a front panelwas placed on a table, and a daylight straight tube fluorescent desklamp (manufactured by NEC Corporation, three wavelength neutral white)was disposed with a height of 40 cm from the table.

Under the light from the fluorescent lamp, the surface of the frontpanel was visually observed from various angles, and the change in thecolor tone of the reflected light depending upon the visual observationangle was evaluated.

The angle dependence was evaluated based on standards ∘: the color toneof the front panel surface was monochromatic (mainly blue or the like)when visually observed from any angle, or the change in the color tonewas gradual even when the visual observation angle was changed by over10°, and x: the color tone of the front panel surface was changed whenthe visual observation angle was changed within a range of at most 10°.

(Dynamic Friction Coefficient)

The dynamic friction coefficient was measured by using a surfaceproperty measuring machine (manufactured by Shinto Scientific Co., Ltd.,model: Type 38) under the following conditions.

First, a wiper (manufactured by Asahi Kasei Corporation, tradename:Bencot) was fixed to an indenter (the area of contact with a sample: 10mm×30 mm), and then the indenter was brought into contact with the frontpanel placed on a stage of the measuring machine. In a state where aload of 500 g was applied to the indenter, the stage on which the frontpanel was placed was moved so that the front panel surface was slid fivetimes with a sliding rate of 500 mm/min with a stroke of 20 mm, and thefriction was measured by strain gauge at the bottom of the indenter. Theaverage of coefficients of friction calculated from the measured valuesof the friction and the load applied to the indenter, was regarded asthe dynamic friction coefficient.

(Static Friction Coefficient)

Using the same apparatus for measurement of the dynamic frictioncoefficient except that the indenter used for measurement of the dynamicfriction coefficient was changed to an iron ball, the front panelsurface was slid under the same conditions, and the friction coefficientcalculated from the friction measured when the iron ball started toslide was regarded as the static friction coefficient.

(Water Contact Angle)

About 1 μL of a pure water droplet was placed on the surface of thefront panel for a touch sensor, and the water contact angle was measuredby a contact angle meter (manufactured by Kyowa Interface Science Co.,Ltd., apparatus name: DM-051).

(Sensitivity of Touch Sensor)

A copper conductive tape was bonded to four sides on the rear side ofeach of the front panels 1 to 11 for a touch sensor, and a voltage of 2kV was applied at a frequency of about 400 Hz.

The surface of each of the front panels 1 to 11 for a touch sensor towhich electricity was applied, was traced with a fingertip, and touchsensor sensitivity was evaluated by the level of the sense of touchperceived by the fingertip. In Table 2, ∘ represents that the sense oftouch was clearly perceived by the fingertip, and x represents that nosense of touch was perceived by the fingertip, or even if perceived, itwas very weak, or the sense of touch perceived by the fingertip was sointense that the fingertip was excessively stimulated, and noappropriate sensor sensitivity was obtained.

The sensor sensitivity was evaluated at an applied voltage of 2 kV,since when the voltage was supplied with an applied voltage within arange of from 750 V to 100 kV to a sample having a PET film with athickness of 10 μm bonded to a copper film, the sense of touch appearedat about 2 kV.

TABLE 1 High resistance layer Barrier layer Insulating layer Waterrepellent layer Layer Thickness constitution Thickness Layerconstitution Thickness Layer Thickness Layer constitution (target) [nm](target) [nm] (constituting material) [nm] constitution [nm] Ex. 1  A120 — — B1 10 — — (Tin oxide/titanium oxide) (Ultraviolet curable resina1) Ex. 2  A1 20 — — B2 10 — — (Tin oxide/titanium oxide) (Ultravioletcurable resin a2) Ex. 3  A1 20 — — B3 5 — — (Tin oxide/titanium oxide)(Thermosetting resin b1) Ex. 4  A1 20 C1 20 B2 10 — — (Tinoxide/titanium oxide) (Si target) (Ultraviolet curable resin a2) Ex. 5 A1 20 C1 20 B5 10 — — (Tin oxide/titanium oxide) (Si target)(Ultraviolet curable resin a3) Ex. 6  A2 20 C1 20 B4 0.1 D1 15 (Tinoxide/titanium oxide) (Si target) (Si target) Ex. 7  A3 100 C2 70 B40.09 D1 15 (Tin oxide/titanium oxide) (Indium oxide/ (Si target) siliconoxide) Ex. 8  A2 20 C1 20 B4 1 D1 15 (Tin oxide/titanium oxide) (Sitarget) (Si target) Ex. 9  A1 20 C1 20 B2 10 — — (Tin oxide/titaniumoxide) (Si target) (Ultraviolet curable resin a2) Ex. 10 A2 20 C1 20 B40.1 D1 15 (Tin oxide/titanium oxide) (Si target) (Si target) Ex. 11 A415 C1 20 B1 10 — — (Gallium oxide/indium oxide) (Si target) (Ultravioletcurable resin a1)

TABLE 2 Angle Water Luminous Luminous Surface Touch Indentationdependence Static Dynamic contact transmittance reflectance resistivitysensor modulus of reflected friction friction angle [%] [%] [MΩ/□]sensitivity [GPa] color coefficient coefficient [°] Ex. 1  90 7 50 ∘ 3.8∘ 0.10 0.09 90 Ex. 2  90 7 50 ∘ 3.8 ∘ 0.13 0.09 92 Ex. 3  90 7 50 ∘ 4.5∘ 0.13 0.09 91 Ex. 4  90 7 48 ∘ 3.8 ∘ 0.13 0.09 90 Ex. 5  90 7 48 ∘ 3.8∘ 0.11 0.09 90 Ex. 6  94 0.5 48 ∘ 55.8 ∘ 0.13 0.07 112 Ex. 7  — *₁ — — —— — — — — Ex. 8  90 7 48 ∘ 55.8 x 0.13 0.07 110 Ex. 9  90 7 48 ∘ 55.8 ∘0.25 0.18 20 Ex. 10 94 0.5 48 ∘ 55.8 ∘ 0.13 0.07 112 Ex. 11 80 15 0.7 x3.8 ∘ 0.13 0.09 110 (*₁ ″—″: no evaluation results obtained.)

As evident from Table 2, in Examples 1 to 10, the high resistance layerhad a surface resistivity of from 1 to 100 MΩ/□, whereby a favorablesensor sensitivity was obtained, and the luminous transmittance was atleast 85% and the luminous reflectance was at most 7%, whereby excellentvisibility was obtained.

Whereas, in Example 11, the surface resistivity was 0.7Ω/□, whereby thesense of touch perceived by the fingertip was excessively high, and noappropriate sensor sensitivity was obtained, and further, the luminoustransmittance was less than 85% and the luminous reflectance exceeded7%, whereby the visibility was poor.

The entire disclosure of Japanese Patent Application No. 2011-283808filed on Dec. 26, 2011 including specification, claims, drawings andsummary is incorporated herein by reference in its entirety.

1. A touch panel interface device comprising: a display screen; and atouch sensor with a front panel that is positioned to be touchable by abody member and that comprises: a transparent conductive electrode; atransparent insulating layer; a transparent substrate between thetransparent conductive electrode and the transparent insulating layer;and a high resistance layer between the transparent substrate and thetransparent insulating layer and having a surface resistivity that isbetween 1 and 100 MΩ/□; the front panel having a luminous transmittancethat is at least 80% of light from the display screen.
 2. The touchpanel interface device of claim 1, wherein the front panel that istouchable by the body member has a touchable exterior surface with astatic friction coefficient that is at most 0.2.
 3. The touch panelinterface device of claim 1, wherein the front panel that is positionedto be touchable by the body member has a touchable exterior surface witha dynamic friction coefficient that is at most 0.2.
 4. The touch panelinterface device of claim 1, wherein the front panel that is positionedto be touchable by the body member has an indentation modulus of atleast 2.5 GPa.
 5. The touch panel interface device of claim 1, whereinthe front panel that is positioned to be touchable by the body memberhas a luminous transmittance that is at least 85%.
 6. The touch panelinterface device of claim 1, wherein the front panel that is positionedto be touchable by the body member has a luminous reflectance that is atmost 2%.
 7. The touch panel interface device of claim 1, wherein thefront panel that is positioned to be touchable by the body member has atouchable exterior surface with a water contact angle that is at least80°.
 8. The touch panel interface device of claim 7, wherein thetouchable exterior surface of the front panel includes an outer surfaceof the transparent insulating layer, and the outer surface of thetransparent insulating layer has the water contact angle that is atleast 80°.
 9. The touch panel interface device of claim 8, wherein thetransparent insulating layer with the water contact angle that is atleast 80° includes a fluorinated polymerizable monomer.
 10. The touchpanel interface device of claim 9, wherein the fluorinated polymerizablemonomer in the transparent insulating layer of the front panel is atleast one of perfluorohexylethyl (meth)acrylate or perfluorobutylethyl(meth)acrylate.
 11. The touch panel interface device of claim 9, whereinthe fluorinated polymerizable monomer in the transparent insulatinglayer of the front panel is represented by:CH₂═C(R⁶)COOX³R^(f) wherein R⁶ is a hydrogen atom, a methyl group, or atrifluoromethyl group, X³ is a C₁₋₆ bivalent organic group, and R^(f) isa C₄₋₆ perfluoroalkyl group.
 12. The touch panel interface device ofclaim 7, wherein: the front panel further comprises a water repellentlayer that is separated from the high resistance layer by thetransparent insulating layer, and the touchable exterior surface of thefront panel is an outer surface of the water repellent layer, and theouter surface of the water repellent layer has the water contact anglethat is at least 80°.
 13. The touch panel interface device of claim 12,wherein the transparent insulating layer in the front panel contains nofluorinated polymerizable monomers.
 14. The touch panel interface deviceof claim 13, wherein the transparent insulating layer in the front panelis devoid of perfluorohexylethyl (meth)acrylate and devoid ofperfluorobutylethyl (meth)acrylate.
 15. The touch panel interface deviceof claim 1, wherein the transparent conductive electrode in the frontpanel has a thickness that is between 50 and 500 nm.
 16. The touch panelinterface device of claim 15, wherein the thickness of the transparentconductive electrode in the front panel is between 100 and 300 nm. 17.The touch panel interface device of claim 1, wherein the high resistancelayer in the front panel has a refractive index that is between 1.8 and2.5.
 18. The touch panel interface device of claim 1, wherein the highresistance layer in the front panel has a thickness that is between 5and 100 nm.
 19. The touch panel interface device of claim 18, whereinthe thickness of the high resistance layer in the front panel is between5 and 30 nm.
 20. The touch panel interface device of claim 1, whereinthe high resistance layer in the front panel includes titanium oxide.21. The touch panel interface device of claim 1, wherein the transparentinsulating layer in the front panel has a refractive index that isbetween 1.3 and 1.8.
 22. The touch panel interface device of claim 1,wherein the transparent insulating layer in the front panel has a volumeresistivity that is at least 10¹⁰ Ω·cm.
 23. The touch panel interfacedevice of claim 1, wherein the transparent insulating layer in the frontpanel includes a cured product of an ultraviolet-curable acrylatecomposition.
 24. The touch panel interface device of claim 1, whereinthe front panel further comprises a barrier layer of silicon oxynitridebetween the transparent substrate and the high resistance layer.
 25. Thetouch panel interface device of claim 1, wherein the front panel furthercomprises an adhesion layer including3-methacryloxypropyltrimethoxysilane applied to the high resistancelayer.
 26. An apparatus comprising: means for producing a front panelfor a touch sensor by: providing a transparent conductive electrode anda high resistance layer on opposing sides of a transparent substrate,the high resistance layer having a surface resistivity that is between 1and 100 MΩ/□; and forming a transparent insulating layer on the highresistance layer, the produced front panel having a luminoustransmittance that is at least 80%.